I used dd-wrt for a couple years on my wrtsl54gs.It was running a bit choppy.
I'd reboot my router about once a week because it would have crashed. Figured
it must have been some harware issue.
Replaced it with a more basic wrt54gl running stock firmware, it worked okay,
but the speeds seemed a bit slow, the dhcp server chugged along, but wasn't
overly happy with it. Ran it on stock for a couple months, but then decided to
try tomato.
About a year ago I dug out my wrtsl54gs and decided to try tomato on it. Mostly
out of curiosity. Since then I've only rebooted my router maybe twice, while I
was moving equipment around due to swapping ISPs (re: Canadian [Shaw] UBB).
I was disillusioned by the fact I was running homebrew software, thinking it had to
be a hardware issue. Tomato just runs so much more stable on my router.
TL;DR - DD-WRT ran like crap on my router, Tomato has been solid.