Well, I'm typing on a Unicomp right now. Its actually quite nice; a bit noisier than the classic Model M, an the keys require just slightly more pressure, but apart from that they're pretty much the same. Some folks will argue with me on that point, but as the owner of a Unicomp Endura Pro (basically, a Classic inside a slightly smaller chassis and with the trackpoint), a 1987 Model M, and an early nineties IBM Ambra quiet key Model M, all of which are used regularly they're all the same... And, they're all different. Each has a slightly different take on the basic buckling spring mechanism. I'd say the Model M is my fave, then the Unicomp, then the Ambra.
I'd say buy one and find out. I got the black case with the oversized lettering on the grey keys. Its quite nice. They also have some different color legend keys on their odds and ends page; really white and grey keys with the printing in various colors, plus some other variations that I'll be getting soon, myself. You can never have too many Model Ms, the father of all keyboards.