my freind has that exact same chainwheel in 30t, he likes it, and the only complaint he has with it is that it doesnt fit his 22mm spindle on his new Primo hollowbites AND for some reason his Shadow chain has messed up the inside wall of the "gaurd" part, because it didnt fit too well when we installed it, so if you decide to get one (despite what beerman said about how you dont need a gaurd if your going to have sucha small sprocket) then dont plan on getting the Shadow chain or any other chain with half or bigger links...
oh and as far as keeping pants out of your chain, it does work for that, but then again, so does having a smaller sprocket...