Bandwidth usage may be significantly decreased with 0.5.0, but it's still too early to know for sure.
One thing in particular that I noticed in 0.4.4 was that every client was sending out a position packet to every other client in the zone every 0.25 seconds - in addition to sending it out whenever a client moves. The position packet was only 18 bytes, but with the overhead of all packet headers and their ACK responses (didn't check if this packet had an ACK), that's quite a bit of bandwidth.
The new algorithm in 0.5.0 is still being fine tuned, but right now, it only sends out a position update when someone moves. In conjunction with the compression of larger packets, I think this will significantly cut down on bandwidth requirements.
As far as RAM requirements go - I think people that get more than 1gb for their home machines are crazy
What kind of applications are you people using that eat up that much memory?!