I went to great lengths to back-grade my old HP DV9000 from 2007 back to XP from Vista and though I had to find drivers all over the world (some countries insisted on XP as an option so the drivers had to be available).
I do own a MacBook Pro for the iOS App I'm trying to build (help required!) but my main machine is a sturdy Desktop with max RAM which I built in 2006 and is still snappy and as fast as I need. Windows open instantly (except photoshop which takes a few seconds) and it really does feel comfortable.
If it's doing everything I need, why upgrade? I'm still able to support members who use Win7 and my old skills as an MCP still apply even today. I think with XP computers became as fast as they need to be. How much faster than instantly can a window open anyway?
The only thing I think I'm missing is the graphics and of course the security of updates as people find new ways to hack us old fogies. I used to love me a good shoot-em-up and this old ASUS board has it's limits (GeForce 7800 GTX) but as long as Serious Sam (any version) still works and I can kill things when I have to I'm happy.
So, are you still on XP? Why? If it's because you love it - welcome to the "Vintage OS Operators Club"