I would like to use a RB153 as an AP with 3 senao 2511 running 120 sectors. I will probably have about 15 clients per card with total throughput around 1.5mbps. I have noticed a lot of people saying the boards reboot a lot and am a little weary of implementing this. Is there a hardware issue with the board or are these people just isolatated issues.

I would venture to say you would be far better off using a 532 routerboard with two Ubiquiti SR2's and two 180 degree sectors...