Presumably, you meant 802.11g?

I've got a Linksys WRT54G. It works fine with the 802.11b WiFi adapter in my laptop. It also works fine with Hugo's Linksys WET11 -- which I've borrowed in order to connect my PCs (upstairs) with the router (downstairs).

Note that the WRT54G doesn't actually implement 802.11g, because it was still a draft standard at the time. It implements what Linksys are calling Wireless-G; presumably they'll release a firmware upgrade soon for full 802.11g compliance (if needed).

I can't comment for speed/number of users, because it's only got my cable modem on one end, so I can only use 1Mbps anyway. Also, I'm not using it with any other -g equipment.

But I can confirm that it interoperates with 802.11b stuff fine, it seems.

I would, however, caution you that Linksys support is a shambles.