I flashed my AR430W (same thing as DIR-300) from OpenWRT to Gargoyle using FON Flash, and briefly loaded DD-WRT as an intermediate step per the DIR-300 flashing instructions on this site. The router works great and now I have wireless bridge functionality, which is what I'm using now.
I'm running 1.0.12, accessing the router over HTTP from a LAN port, and if I press and hold the refresh key for 15 or 20 seconds, I can make the router reboot: The light on the LAN port where my PC is plugged in goes dark and then a little bit later the router flashes its LAN port lights in the familiar 4-3-2-1 pattern I'm used to seeing at router boot-up.
I don't know if this happens with OpenWRT or not. Since Gargoyle has wireless bridge, I likely won't go back to OpenWRT soon.

Thanks for your efforts!
-katapaltes