My company (large software company) issued an edict that all computers running Windows XP would be upgraded to Windows 7 or retired by the end of 2013. My laptop running XP was upgraded to Win 7 several months ago. I still need to test our software using XP but we have VMs for that.
At home, I had 2 older computers still running XP that I gave away just today.
There's nothing I could do with XP that I can't also do with Win 7 or 8.
The only software I used with XP that I couldn't use with Win 7 was some backup software. The only software I used with Win 7 that I couldn't use with Win 8 was, again, backup software.