Nobody has had performance gains with that switch, unless there was another issue. Windows 8 x64 is very slow on 1 GB of ram. I installed it on a 1 GB laptop and it ran very poorly. Much worse than windows 7 or XP did. I would no recommend it.
I guess it doesn't hurt to try it, if you like experimenting, but I would use 32 bit. It requires less ram. Just be prepared to go back if your not happy.