Maybe it's just me, but on several occasions I've gone back to (uncommented) code I'd written several month or years ago, and thought "what the hell is going on here? Who wrote this shit?" Those time I really wish past me had taken a few seconds to write out exactly why he had solved that particular problem in that particular way, despite how obvious it no doubt seemed at the time. There are few things more annoying than finding some 'ugly' code, fixing it, having a bunch of stuff subtly break and then finally remember that there was a very good reason why you originally wrote the code the way you did. If only I'd left a comment of two for future me, much time and anguish could be saved.