It all depends on your technical abilities!
I am currently using v4.7.0.141 (platform 4.0.0.174) which is very stable and faster with the accelerometer (the turning the phone on its side thing) the battery life is also better!
Just go to
http://www.crackberry.com, go to the forums and find the 9500 upgrade (UK model) or 9530 upgrade (US model)
Download the file, then disconnect from the tinterweb completely, then open up and install the file you have downloaded, then open Blackberry Desktop Manager which SHOULD notice an update installed then ask you if you wish to install it.
Good luck.