Tomato is nice and super easy, it's basically DD-WRT dumbed down to be close to factory firmware (but still retains some amazing capabilities). I have used this on a pair of Buffalo routers to bridge a huge property, it's been fantastic. Support? Um.. Hello? Anyone home?
Personally, I liked Open-WRT the best, it just seemed more polished while retaining capabilities. The bad part is that it doesn't support as many devices and has a smaller community behind it than DD-WRT.