Of course, you only need a single Google Reader app and I'll help you choose between two that claim to be everything that you need.
BerryReader (BR) is developed by Bellshare and is currently in stable version 1.0.63 for OS 5.0. It is available for numerous devices and OSes and currently costs $9.95 from Mobihand, though it was on sale on 9/10/10 for $4.99 from App World - so deals can be found. Unlike many developers, Bellshare offers a 7 day free trial as well.
Feeds (Feeds) is developed by CDJ Studios and is available for $2.99 on Blackberry App World. The current version is 1.01.