Well, just two weeks ago I had a Female Spotted Bristlenose and Rubbernose Pleco come down with Ich. A VERY minor case, mind you, but it was definitly Ich. I must say though, that my Male Common Bristlenose and my other Spotted Bristlenose didn't show any signs
Luckily the tank I keep my Common in has never come down with Ich, so I can't tell you anything on that one