You need to think very carefully before switching digital asset management platforms.
Both A3 and LR3 are full fledged RAW editors (LR3 maybe even more so, as more of Photoshop's features are integrated into it) as well as photo databases. The changes you make to your photos in one platform won't be picked up in the other. If you're just starting, that's not really a big deal. If you have a huge catalog of photos... you can imagine.
Honestly, I'd rather switch camera systems than switch DAM software.