i also have one of these routers and would like to know the process of going back to the manufacturer firmware, im not having any problems with it but just incase
I have two wrt150n --- both were flashed to dd-wrt (one as a AP and the second one as a repeater bridge).
But the dd-wrt firmware doesn't play nice with auto channels --- always put my router on channel 14 so I flashed one of the wrt150n back to the linksys firmware as a AP.
Just do a 30-30-30 reset before you flash it to the linksys firmware and do it with internet explorer (not firefox).
You can flash the wrt150n with the original linksys wrt160n firmware --- read the readme file and you will find that the 1.02.2 firmware for the wrt160n is compatible with the wrt150n. I have done it --- and you will have the top "reserved" button working for auto WPS setup and support for LELA 3.0.