1. Offers nothing over Windows' functionality.
If you are already proficient in your Windows OS, it's probably best to stick with what you have. You would be unlikely to gain anything with Linux – except for an unnecessary (and perhaps irritating) learning curve to trod through.
2. Technical hitches are frequent
I can honestly say for the first couple months I probably spent more time trying to fix stuff that broke rather than doing anything productive. The bulk of the headache I endured were mostly attributed to issues I had with properly installing display drivers for my ATI/AMD graphics card which apparently Linux doesn't work very well with. Other issues I've come across included Youtube videos that would only display in black & white, getting locked out of my own user account after deleting a different one( having never set up a password), and a more recent problem which prevents me from logging into my yahoo mail when using certain browsers (solution pending).
3. Community support less than stellar.
There are a fair amount Linux forums out there, but what I've found is that willingness to help out isn't really all that great. When it comes to soliciting help, I hope begging isn't beneath you because it might be what it'll take to reel in a Linux nerd. On the other hand, there are FAR more support forums for Windows with volunteers who are generally more eager to provide assistance. Add that to the fact that a majority of tech issues (even complex ones) can simply be googled and solved in mere minutes. It seems puzzling that Linux advocates would even bother citing community support as any kind of “advantage” over Windows.
4. Won't play nice with your existing Windows network
Assuming your computer is on a Windows network, you might want to take note that Linux won't work easily with it. First you'll have to install a program called “Samba” and even then you won't be able to access your Windows PC's without finding and editing system files which might not be a huge problem for techies but could prove quite burdensome for the average layman. Also, it's worth noting that any adjustments made to enable network functionality could easily be undone with either a Ubuntu or Windows update that changes firewall, and/or security settings. You'll be back at square one.
5. Sudo what!?
As mentioned earlier, it's fairly likely that you'll run into frequent technical hitches especially if you aren't already familiar with the OS, and when you encounter them, more often than not you'll be required to use the terminal which is basically the Linux counter part to Command Prompt in Windows. I'm well aware that high to moderately skilled techies won't have much of a gripe entering command lines to fix problems every so often, but we're talking about the average computer user here. It's hard to imagine why someone already acquainted with Windows' user friendly GUI having to constantly hunt for terminal commands they won't remember nor playing the role of a beggar in a Linux community “support” forum thereby delegating their day's work schedule to the whims of Linux geeks who aren't always eager to leap to the rescue.
6. Not a great option for Multimedia buffs
You enjoy watching high definition videos on the Internet or Blu-ray movies on your PC? If so, count Linux out. From my experience, videos always ran much better on Windows than on Linux especially with respects to on-line flash video. If you have a newer computer then perhaps the decrease in performance won't appear drastic, but for those of you with older processors such as mine (Athlon 64 2.4Ghz), you're far better off sticking with Windows. Also, keep in mind I tried both open source and proprietary video drivers. Neither proved much better than the other.
7. Stuff breaks far too easily
I've already said my piece on the frequency of technical hitches; however, another point to be made is the sheer ease at which the OS keels over. For instance, something as simple as uninstalling and reinstalling a video driver via the GUI caused my graphics to completely fail upon reboot. I wasn't even able to access low graphics mode. It took me over a week of troubleshooting via Google and forum begging before I finally discovered a solution. In another situation, Ubuntu failed to boot after I had added an additional hard drive. Apparently after every added storage device you must manually edit settings in the GNU Grub menu to re-identify which drive Ubuntu launches from. Yeah, convenient right?
8. Gamers need not apply
This one is already well known, but it's a significant shortcoming nonetheless. Linux isn't well suited for gamers or any other computer user who uses graphic intensive software for that matter presumably because of poor video driver support as well as the lack of software development for the Linux platform. Linux's meager market share renders software ports an unworthy investment for developers which leads to my next point...
9. Weak software and service compatibility
Are you a heavy Microsoft Office user? Love your Itunes? How about Netflix? Well you'd be out of luck with all three of these program/services because Linux doesn't support them; in fact, it's probably safe to say that most programs & services on todays market aren't compatible with Linux. You'll most likely have to settle for open-source alternatives.
10. You get what you pay for (or don't pay for)
Linux is a free OS which means its competitors have an immediate advantage at least in one respect –resources. Open -ource software is great, but it can only compete on so many levels with its very well funded rivals. I don't want to make too much of a fuss over this because much of it is common sense, but the fact of the matter is that most computer users have grown accustomed to using premium software with features and technical support superior to that which their open-source counterparts offer. The open-source community deserves a ton of credit for their generous contributions, but the question is whether or not users can cope with less bells n whistles and grow equally accustomed to a no-cost trimmed down alternative. I have a feeling many people could, but I also have a feeling most couldn't.
Now its not to say that Linux is without purpose, because it certainly has its uses, and with a price tag of free I couldn't possibly conceive of a better offering. However, I also think it's important that we don't get carried away by accidentally over-stating Linux's advantages over Windows. Contrary to the brash exaggerations from overzealous Linux fanboys, a decision to switch to Linux is one that should be made with careful considerations and thoughtful contemplations of the pluses & minuses whilst also bearing in mind your particular needs and intentions. My final impression leads me to conclude that casual computer users who mainly intend to perform basic tasks such as web browsing, email, word processing, etc stand to gain the most from Ubuntu because they'll experience virtually no learning curve since performing basic tasks are just as easy in Linux as they are in Windows and such users will also reap the benefits of not having to deal with all the security issues and malware threats Windows is notorious for. On the other hand, users who use specialized programs and have grown reliant on specific features in their daily applications might have a much more difficult time adjusting to Linux especially if he/she isn't necessarily a “tech wiz”. Unfortunately, I believe the profile of the average computer user is increasingly resembling the latter which means in most cases it might not be a good idea to recommend the switch. Of course there are also experienced users who are familiar with the ins and outs of computers yet haven't bothered much with Linux, such as myself, and while those like me might encounter plenty of frustrations at first, we're the ones best suited to adapt and eventually appreciate Linux's offerings. But from the perspective of the average joe or jane, it's not immediately apparent to me how Linux is somehow this glorious answer-to-all solution that many like to portray. So as a rule of thumb, if you are already plenty happy with what you already have –don't even bother with Linux. Save for a headache or two, you probably won't stand to gain much, but if you've just about had enough of Windows and your actively seeking something new, then you might as well give it a try. What is there to lose?