they're a somewhat popular pleco for the planted tank. they don't get nearly as large as *most* plecos... they stay closer to the size of a clown pleco or bristlenose pleco (several sites say about 6"). as for algae consumption... i've never bought a pleco as an "algae eater". they do consume algae from the glass and driftwood, but as much of their diet comes from scavenging (feed sinking wafers) and vegetable matter (blanched zucchini, etc) as well as cellulose from rasping on driftwood. my plecos rarely graze algae during the da or night. the rubbernose might be a better algae eater than clowns or bristlenoses (the plecos I keep), but my guess is it will be pretty similar. If you want an algae eating fish, get 10 otos, if you already have otos, get 10 more
if you're tired of otos, get a pair of SAEs. if that doesn't suit you either, do more water changes :P
seriously though, I think everyone needs a pleco or two, just for the fun of if, and rubbernoses are really nifty plecos at that. plecos are funny fish, great scavengers, and as a bonus they'll graze on algae (they'll probably keep any driftwood SPOTLESS), but they are not an all-encompassing solution to algae in the tank.
edit: p.s. they shouldn't be destructive to your tank or your discus. all around easy-going fish.