the only snail i like is my assassin snail Beowulf, because he eats the damn pond snails that infest our community tank. it's fun to watch him hunting them, creeping up on the glass behind them and then pouncing them in slow motion.
pond snails are really annoying, but a few weeks ago they gave us a good "early warning" message. when the frog-food fiasco happened, the first sign of a problem we saw was all the pond snails congregating above the water line, and figured there must be something wrong with the water if they all collectively ran away from it. luckily we got it taken care of before any of the inhabitants we WANT in there were hurt.