Mine is in for warranty. The top mounted battery compartment seems to be problematic for myself and others (google it, kept popping off after about 5 shots for me). They moved the cover from underneath in the FFII to ontop so you wouldn't have to rezero when you put in a new battery. As such, a FFII may be a better deal especially if you can get one at a discount.
I have a sparcII and a trs-25 as well. Both good solid red dots I haven't had any problems with. Perhaps not as fast as a pure reflex sight but with a bit of practice you are on target v. quickly. Vortex has a warranty center in Guelph and a lifetime transferable warranty. Bushnell warranty is good for a year.
I can't wait to get my Fast Fire III back so I can say good things about it and Burris forever warranty. ATM, all I can say that shipping UPS to Colorado isn't cheap.