Is this not enough documentation? DD-WRT Docu (EN) - WRT Wiki
Actually the DD-WRT works great on:
The issue with the versioning is it has to be Version 3.1 or earlier (I was lucky to have a Verison 3.0 from waay back before I started). With Version 4 and 5 versions of the WRT54G*, Linksys greatly reduced the amount of RAM in these units, which severly limits the "extra" things you can do with DD-WRT. Like the Sputnik and RADIUS support (for Hotspots/coffee shops), VoIP and other features.
But there a "MICRO" build version of the DD-WRT firmware that will fit on these version 4 and 5 routers by stripping out all of the features we all like. Just without the cool extra options. Version 7 is not supported (at this time).
One of the main benifits, even with the Micro build, of going with DD-WRT was to have Wireless Bridging, and Wireless Client Bridging - this allows you to not have to run CAT5 in your house. There's also WDS which is suppose to be the norm now for bridging, but I haven't had any experience with it yet.
Using Wireless Bridging you can connect two opposite corners of your house, without cabling (just need to run a cable from the remote router to your desktop in the corner, like 3').