I recently replaced my WRT54G running Tomato as well.
Got a
Netgear WNDR3700, has gigabit, USB, dual stream 802.11n and simultaneous 802.11g. I like it quite a lot and OpenWRT Backfire is pretty polished too, the web interface makes it all fairly easy like Tomato.
I picked one up this morning. The web UI's not quite as slick as Tomato (probably because it exposes a lot more options), but it was pretty easy to configure (apart from needing to use failsafe recovery at one point -- my fault), and it seems to be working fine.
Because of it, I've managed to decommission the WRT54GL, a Netgear GS108 switch and the Netgear ADSL router that I've been using as a wireless AP. Win.