After using the lovely Mach3 for two or three years, I recently read that razors with multiple blades actually do much more harm than good to my skin. I'm prone to develop razor bumps (which I didn't think increased with my use of the Mach3, just maintained the status quo ... I guess), so I've made the switch to Bic Sensitive single-blade disposables. The shaves certainly aren't as smooth, but I think I'm doing the right things for my skin. Sure I still have razor bumps, but I'm absolutely certain that the situation isn't getting any worse. :/
-SUO, between shaving's a rock and a hard place