I don't think I want to tackle the "should I" part of this, but here has been my experience so far:
I did an upgrade install of XP (I wasn't sure if I wanted to keep it)  
First, I ran the compatability program on the CD and uninstalled the things it said wouldn't work
or might cause problems.
Then I let it do it's stuff.  I moved all my icons to one side of the screen and one by one tried each.
Some of them ran right off the bat, and some needed to be re-installed. but eventually, every item
I have worked (with minimal effort from me)
I have had it on for about a month now.  I saw small (insignificant) decreases in some benchmarks
(primarily 3DMark2001 which was about 200 points out of over 7000).  No problem with this
We game here alot (oh yeah, I am really describing two computers which are identical in terms of
hardware).  I am nothing but pleased with the XP.  It is soooo stable compared to my old 98 (SE)!
When a game does crash I am only sent back to the desktop (every once in a while, I have to hit 
cntrl-alt-delet and end the task) and to resume play I just double click the icon again.  We virtually
have eliminated re-booting all together.  I love this!  Not only are game crashes MUCH less severe,
but they are also MUCH less frequent then they used to be.
To sum it up, I had no confidence originally, and ghosted a copy of my HD to a second HD so I could
easily go back to my original set-up if it was necessary.  Well, I'm ready to take that second hard drive
and start experimenting with Raid (I want to do a clean install, take advantage of NTFS format and
get this puppy set for the long haul.....  I'm sold!