I have a couple bristlenose plecos (L144 I believe; they only get to about 2 - 2.5" long). I hardly ever see them on the glass except when my lights are off. They do a decent job, but a few more would be ideal if I weren't already overstocked and had a bunch of females holding. My tank is a 90 gallon mbuna tank.
I wouldn't recommend the trumpet snails because they have had the tendencies to overtake my tanks (reproduce like crazy and I don't like having to fish them out every month or so). I have read that olive nerite snails are ideal if you want a limited number of snails in your tank: they need brackish water to reproduce, so you have a better control of snail population in your tank.
^ i agree