I'm upgrading to a mix (whatever I can get on eBay) of SRAM Force and Rival on my drive train (shifters, ders, cassette and chain). I can't seem to find the 11-28 cassette anywhere (I currently run a 12-27 with a 50-34 crank and am looking for a little easier spin on some big hills). Anyone have any experience running the 11-28? Is it no good? Shifts poorly?