I have been running DD-WRT on my routers for a long time. My router of choice as of this writing is the Asus RT-N16.
It is gigabit, has a fast processor, and 128 Meg of ram. The only downside to the router is that it does not have a 5 Ghz radio.

An interesting note:

ASUS made an interesting choice for their component selection. The RT-N16 is powered by a Broadcom BCM4718 Intensi-fi XLR 802.11n Simultaneous Dual-Band (2.4/5 GHz) Router System-on-Chip. This chip combines the baseband, MAC, 533 MHz CPU and radio modules and includes the USB support found on the RT-N16. Although the BCM4718 has a 5 GHz radio, ASUS didn't put the circuitry in to support it. So even if you load up the DD-WRT distro, you won't get a dual band router.
Installing DD-WRT onto the RT_N16 is easy. Follow the directions here, and then make the changes I describe below to set the wireless up correctly.
My Current network consists of the Asus RT-N16 as the main router, with 2 airport expresses being used to extend the range of the wireless network. Everything that can be wired has a cable run to to. I wired the complete house for Gigabit ethernet. The wireless is only for the mobile devices.

Adding 5 GHz Service to the network:
To provide 5 GHz service I use an Apple Airport Express locked down to the 5 GHz band. This works well, and lets me put it where the laptops are used the most. I also have an older airport express providing 2.4 Ghz service on the 2nd floor.



Getting the most out of route RT-N16:

If you are using 802.11N you must use WPA2 Authentication with AES or no security at all if you wish to achieve N rates. Any other setting will result in the client falling back to G rates per the N specification.

Also do not turn off WMM. It is requited to be on for any certified N product, and some clients will complain if you turn it off.