I've always though the biggest strike against using custom/open firmware was the lack of support and potentially voiding warranty.
Buffalo Technology - Press - Press Releases - BUFFALO AND DD-WRT COLLABORATE TO CREATE THE MOST COMPREHENSIVE CONSUMER AND SMALL BUSINESS WIRELESS OFFERING
The WZR-HP-G300NH can be had for under $90 here in Canada, NCIX just had it on sale last week for 84 when I picked it up. Gigabit, Wireless N, high powered radio. Review here.
Buffalo Nfiniti Wireless-N High Power Router & Access Point Reviewed
I imagine you wont see it on the shelf with DD-WRT for a while. Its a really easy flash with the web wizard.