I use a D-Link DGL-4300 as my router. I have a Linksys WRT54G running DD-WRT as a wireless client bridge (and a Netgear WGPS606). I used the WRT as the main router previously.
IMO the D-Link is a superior router.
It has a superior feature set to the Linksys out of the box (and is in some ways still superior to the DD-WRT). Buffalo out-of-box feature set looks better than Linksys. I've even heard of wireless client bridging being available out of the box, but I didn't see that in the manual. Buffalo wireless is said to be better than Linksys.
The D-Link is fast and stable; it's never crashed or locked up on me, which is something that I can't say of the WRT54G routers that I've used for long. I've also had 3/4 Linksys power supplies fail over time (years).
The wireless on the D-Link is nothing special. The value proposition of this router is mainly the fast & stable router + feature set + built-in fast GbE switch (although it doesn't support jumbo frames, which are not critical with fast modern gear).
If I was buying a new one, and had lots of money to spare, I'd be tempted to get one of the new draft-n gigabit routers (D-Link and Netgear have them; Linksys and Asus don't AFAIK). The biggest problem with these is the 802.11n is not yet finalized, and so anything you buy now might not be upgradeable to the final standard. So far, AFAIK, only Asus has committed to being upgradable to the final standard, but they only have 100 Mb/s wired ports, which don't make much sense on a wireless device that's supposed to be able to go > 100 Mb/s.
If you're planning to get a wireless router that will be obsoleted before long, then I think the Buffalo / Linksys are the best buys -- at least, they can run 3rd-party firmware that somewhat keep up with the times, and can do cool things like wireless client bridging.