[quote name='SneakyPenguin']Alright, thanks. Is there any way to tell if a WRT54G I'm looking at is one of the gimped ones or not, without actually buying it?[/QUOTE]
Sure, open the box and look at the bottom of the router.
Generally speaking, I think most of the newer WRT54Gs are gimped. Looking here
http://en.wikipedia.org/wiki/Linksys_WRT54G_series I can see that versions of WRT54g through 4.0 had twice the RAM and Flash Memory as the newer models, with the middle batch having a slightly faster processor (216mhz).
If you poke around on the dd-wrt forums, you can see what they're recommending for routers meeting specific requirements.
Part of the issue is if you expect to do heavy downloading (torrents/newsgroups/etc.), as a lot of routers seem to lock up or slow down with the number of connections they need to manage to run that stuff well. Other benefits of dd-wrt include overclocking, signal amplification, etc. If you have everything right by your cable modem though and don't need wireless or you don't put a heavy amount of data transfer on it, you could probably find something solid right out of the box.
For me, with the two consoles, 3 laptops (one being my work laptop which I need to have a great connection since I work with a lot of remote systems), and random other devices, especially when one or two of the laptops are running torrents, I need something more than the stock firmware which tended to choke and constantly required resetting.