I'm running XP pro for about 3 months now, after the hell of ME (which came with my current main computer) it's a BIG improvement, but it still carries a lot of these typical Microsoft quirks
You can't un-install Outlook (which I never use!), and a few days back I created an .htaccess file in Notepad, and XP refused to let me re-name it from .htaccess.txt to .htaccess (had to do it in WSFtp) - just the way Microsoft always knows better what you want to do!!!
Another nuisance: I set up Explorer to open all GIFs and JPGs in ACDsee - no! Microsoft insists to open GIFs in it's own image viewer which is shit...
Work-around: open a JPG first and then start to scroll...
I managed one blue screen of death so far (can't remember how, though) compared with about a dozen it would had been on ME...
Some programs behave strangely, like Paintshop Pro 7 (which I use a lot for my graphics). It handles the memory not as well as under ME, so with a large floating selection it's down to a crawl with half a gig of memory, and with some odd freeware fonts in vector mode I get constant crashes of Paintshop (whereas these gave no problems under ME or 98SE)...
FINAL WARNING: be prepared that you need a lot of hardware resources...