i've had the williams FP on my bighorn almost as long as i've had it (back when you could get them for 30 bucks from numrich arms). its worked well, but it's a little tweaked from a spill i took when i stepped on some loose shale in the blues one year.
i bought an ultralight a little while back and picked up a WGRS sight for it. I like how compact it is, and i don't usually mess with my sights once they're set too much to really need the adjustability of the FP. time will tell, i could always switch them out if needed. i do know that I had to clearance the stock on my bighorn to get a full range of adjustment out of the FP sight.