Thanks guys! Previously, I was able to press both simultaneously. I use screenshots as reminders and trust me. This has changed in 3.1. You have to do a much more definitive Power press before touching Home.
Strange, I can still do it simultaneously and have it take a successful screenshot. This is with 3.1 on a 3G. The funny thing is that it won't take a SS if I press sleep then home. Got me.