A year ago I wanted to try a fixed gear bike like all the cool kids are doing. But being a cheap bastard, I didn't want to pay much. So I bought a frame that turned out to be too small, a stem that turned out to be 26.4 mm rather than 26.0mm (freakin' Italians!), and a crappy fixed rear wheel (a p.o.s. Suzue hub laced with crappy generic spokes to a worthless Sun rim, oh and did I mention that it came with dog poop nuts?). The whole bike was a disaster.
On the other hand, it was superfun and I learned a lot from my mistakes (plus good advice in the SS/FG and Mechanics forums, plus superguru Sheldon Brown) and it allowed me to figure out how to build up a really great fixed commuter and rain trainer. I ride that bike nearly every day and every turn of the pedal is a silent joy. It would have never happened without that first fixie disaster.