We have used DDWRT for over a year now and have never had an prob with it. We run it on a WRT54G that is on and open to the public 24/7. I may have had to restart it 3 times in the last year or so. We frequently have 15-25 wireless users.
There is plenty of support for DDWRT online and I would definitely recommend it. If you have read anything about it you know that it has a ton of features that just arent available anywhere else. (features here http://www.dd-wrt.com/wiki/index.php/What_is_%22DD-WRT%22%3F#Features )
I am also running it at home on the same router, which lives in my HOT attic. The temperature doesnt seem to affect it at all, even under a heavy load.