It's one of the best I've had, second only to my Ciscos. I've had several Netgears, an Actiontec (piece of crap), a Westell (excellent DSL modem/router), a few Belkins (also piece of crap). I have two WRT54G routers, and love them.
Like everything, it all depends on what you expect it to do.
If you happen to know anything at all about unix systems, you might just really love a WRT54G. It's a little 200Mhz MIPS cpu running a Linux 2.4 kernel. Linksys didn't help much, but because it is a GPL'd OS they had to release the source code to the firmware, and now you can get 2 or 3 different third party firmware releases which allow all sorts of fun things to be done. And the more you know about unix systems admin, the more you can do with it.
That said, they are inexpensive new and cost even less if you take the risk and buy a used one on eBay. I picked up a couple of them for $80 total, delivered (about the same cost as a brand new one purchased locally). I had two of them already, but they are dedicated and I wanted two more just to play with... :-)