When I wanted to try 64bit I downloaded Ultimate, but my pc ended up completely freezing way too often a day, causing me to do hard reboots everytime.
Don't do it. I don't know if this is a common thing but Windows 7 Ultimate turned my relatives Alienware M17X with 8GB Ram / quad core, raided for performance on 2 Seagate Momentus 7200RPM discs into a sluggish P.O.S slower than my 3GB ram i5 (no raid) Dell XPS 15.. Reverting back to Home Premium solved it.
Went back to Professional 32bit, not a single problem with any game or whatever you can have a problem with
(Yes my pc IS capable of running 64bit)