You can use the WRT-G and WRT-GS routers if you you use versions 1,2,3,4 and flash the bios to
http://www.sveasoft.com.
The software form sveasoft works great I have 40-43 units int he field.
I use ppoe and works great.
There is one problem. Cisco bought out the Linksys and they have come out with a new WRT-GS router version 5. It is a nutered unit that can not be upgraded because they 1/2 the ram and changed to a new o/s (no longer *nix).
So most people are buying up as many version 1-4 they can get there hands on right now. Sveasoft is now working on other units that can be upgraded to there software (which is every bit as powerfull as Mikrotik now days) And can be upped in power to 251mw.
However, with that said it is not an industrial grade unit which is why I use Mikrotik for all relays and using the wrt at my customers location. I would use Mikrotik if I could afford them.
-Michael