Dear God, I can't stand XP. It really worries me how many people like it.
First off, as a personal opinion, I think it's default look is incredibly ugly, but that is not my main concern...
Check this link to Gibson Research Corporation's page about XP:
http://grc.com/dos/sockettome.htm. The issues brought up here are very serious. In summary, Windows XP Home Edition contains support for what's called "raw sockets", which basically allows data to be sent directly to the file system, bypassing the standards of protocols (which data normally must follow). This has various uses, and has been implemented in *NIX systems for some time. However, it has always be restricted use, only allowing the system to access this feature, as no user should ever need to. However, XP allows ALL USERS access to raw sockets. This is extremely dangerous, as it could allow data to be sent to the machine unchecked. That data could contain malicious code, and the system would simply let it in.
Luckily, Steve Gibson has developed an application to solve this problem, but most people will never know about it. This could easily lead to a new wave of malicious intent on the Internet. "Hackers" will have a brand new toy to play with.
As third concern, I feel XP makes it easier for people to be computer illiterate. I have had this same problem with AOL for quite some time. It has become so user friendly and cute that people will never know what to do when things like blue screens or access errors occur. I don't expect everyone to be computer technicians by any means, but I do more support work for people using AOL and Windows ME then anything else. It's usage is so basic and elementary, that when something out of the ordinary happens, people are completely stumped.
So, overall, I am not too fond of XP. This is all really directed at XP HE, as I have yet to test Pro or otherwise, but I can't say I'm too hopeful.