SMP is an optional component of OTR. The Pidgin plug (I've not used it in a while) gave you a number of ways to verify the other party is the party you thought they were. SMP being one, verifying the other side's public key being the other off the top of my head (the tutorial in the article covers both methods).
Unless you're going to endow some central party as being the ultimate source of trustworthiness (which has worked less than ideally in the case of SSL certificates), there's not too many options that 'simply work'. I'd say SMP is a whole hell of a lot better than trying to verify the other side's public key (since in SMP, you can plan that ahead... you can't verify keys that have yet to be generated).
What scheme would you say would work better than being able to use either SMP or the hashes?