I'm with Mike. I shave 3-4 times a week and my Mach 3 cartridges usually last for a couple months. When they get uncomfortable I replace them. I've had the handle long enough that the cartridge release button has come off and now I have to just yank them off to remove them. So last night I had a post all typed up about why I'll wait until I'm out of Mach 3 cartridges until I try a DE safety razor, but I ended up making an impulse buy on Amazon instead.
We'll see if I end up getting whole-hog into it, but I ordered what is said to be a decent handle (Merkur 1904 classic), a few blades, and an alum block. I'm skeptical about the "quality of shave" argument but I'm going to try to give it a fair shake - which is why I didn't just buy the $6 handle.
I've thought about trying to learn to use a straight-edge razor for a long time, but decided that I don't want to die.