I switched to Ubuntu from XP on Oct 2008. And was running Ubuntu till July 2009.
All described is solely my opinions (yes, biased) and using experience.
Main issues that made me return to XP (not sorted by importance or whatever):
#1
* Lack of user-friendly protection compared to XP’s protection when XP is guarded by CIS or similar software. Yep, I knew about SELinux, AppArmor, iptables, PaX etc.
But i didn’t want to spend dozens of hours to learn this stuff and setting this all up.
I’m still not sure whether iptables (when properly configured) filters packets on application level. I’m still not sure whether AppArmor (being Mandatory Access Control system) can be compared by functionality to HIPS like Defense+ of CIS (despite they are for different OSs).
Besides, I was not satisfied about application-based firewall software i found (FireFlier, TuxGuardian, Linux-Firewall.org). I didn’t like 2 of these were no longer actively developed (FireFlier and TuxGuardian), 3rd i found hard to install and after i installed it, it worked with explicit errors (Linux-Firewall.org).
#2
* CPU usage min 30-40% compared to XP’s 1-2-3% ;
#3
* Mouse right-click issue with Gnome desktop (some report KDE has same/similar issue). See here for more details: 1 2 3
IMO this is not a Desktop usability issue, but OS usability issue.
#4
* I was not able to make Ubuntu cooperate with my Epson scanner.
#5
* It was a hassle for me to maintain dual-boot setup, keep virtual machine and use wine (software not alcoholic drink 
) to run working apps that are for Windows only.
I must say now i would opt out from VM and wine and would use only real XP
#6
* Too much time to spend to learn Linux internals, Bash, specific instructions. Once i realized very often i just want things get done (XP) without any learning steps.
Yes, i want underline that despite Ubuntu “is the most user-friendly”, it was a little shock for me once i realized how much time i spent during these 9 months and continued to spend over and over.
#7
* When I wanted to buy a notebook for myself i realized i need to check Ubuntu’s “supported hardware” list very thoroughly in order to be able to install Ubuntu.
In the end i came to conclusion I’d rather buy notebook with pre-installed Windows.
#8
* Dissatisfactory current status quo with 3rd party apps support.
On Windows i find app i like on the web, get it and install it or move to appropriate folder and run it (if it’s a portable program). if i don’t like what i got i uninstall/delete that app. That’s all.
On Ubuntu i find app i like, but i cannot download it and run because Linux apps are rarely distributed in binary form. So i should check for specially packaged version of this app (to avoid possible problems due to compile errors, compatibility issues with latest version of Ubuntu etc.) in so-called software repository (Ubuntu’s servers with deb packages of applications - servers are accessed with a special program aka “package manager”) - if app is in the repository i’m advised to get it from there though the version of app may be outdated. So i end up with recent/outdated version (depends on “world-wide” popularity of this app - if it is more popular there are more chances i get recent version).
Another scenario if app is missing in Ubuntu’s software repository. Then i need to compile it from source. I may or may not be successful on this. Mostly depends on my compiling skills/experience.
Read this for advanced information: http://autopackage.org/NOTES
#9
* Distribution upgrades every six months.
It was a problem for me. One upgrade was successful (from 8.04 to 8.10) and one failed (from 8.10 to 9.04), i got a damaged X Window system somehow (big lag appeared for some desktop activities), though no errors were displayed ever and my 8.10 was in good state. I then reverted back to 8.10 system image captured before upgrade and ran it till end.
For me this kind of stuff was 50/50 chance of success.
Of course one may choose LTS (Long Term Support) release to avoid frequent OS updates. I have not chosen this way at the very beginning.
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Of course there are many positive and “cash-saving” sides of using Ubuntu vs XP. There are desktop usability features which XP lacks. There are outstanding programs like Dar (Disk Archiver), Transmission, Amarok v1 etc.
Yes, Ubuntu can be used in stable working environment to save money instead of paying for Windows (by stable i mean environment to perform repeated predictable tasks with concrete known ways how this would be done on current version of Ubuntu).
Ubuntu is not a desktop platform for me at the moment despite there is a huge progress in “Linux desktops” segment (Ubuntu, OpenSuSE etc.).
