I would be very curious to know if this is continuing to work well for you. I have the same router and have the exact same problems with the "user freindly" firmware.
I originally tried to set this up with DD-WRT but gave up because I was having trouble firguring out how to set up a guest network. However, with the user freindly firmware installed, I have to reboot the router every day or two to allow machines connected by wifi to work. (However, when it is working it seems to work great.)
If the DD-WRT firmware is more stable, I will put in the effort to get it running correctly.
It seems like other people having the same problem with this router. How come the firmware has not been updated in nearly a year?