Windows 7 is a really good OS but it really depends on your hardware. XP is by far the best Windows OS to this date IMO and while windows 7 is a great OS you need some decent hardware to get it running on your PC.
It depends upon your system configuration, but why to worry when XP is there then i guess no other OP is needed. I prefer XP fastest, best, easiest and common
Windows 7 installed faster and performed faster on both systems than either XP or Vista. Windows 7 should be even more robust and faster than the beta version.
OSX FTW Mac wins out of both these. I used to be a windows fanboy untill I bought my macbook 2 weeks ago :O
XP just works! Although W7 is a vast improvement over Vista and performs as well as XP, it's not as easy to use and configure as XP. The thing that will keep me with XP as long as possible is the very intrusive "security" in W7. I like to run my PCs the way I want, not how MS wants. I won't tolerate all those "Access Denied" messages from my own equipment and having to jump through hoops to get access to my own files, or network 2 or more PCs together.