Nikesh
I have flashed my WRT54G with DD-WRT v23 SP2 micro. I had reliability issues prior to this (dropouts, etc) that have disappeared since I took the plunge. DD-WRT also adds heaps more configuration options, the most useful for me being the ability to change the signal power ouput of the router. My network clients now have a better consistent signal available to them.
I used the guide at
http://www.wrtrouters.com/guides/upgradetolinux/
and found it easy to follow. It also has direct links to all of the downloads you need.
Other useful info available at
http://www.bitsum.com/openwiking/owb...?WRT54G5%5FCFE
http://www.scorpiontek.org/portal/content/view/27/36/
http://www.dd-wrt.com/wiki/index.php...er_Information
HTH
Cheers