We actually mainly stick to one model for everything, and that's the M3045's.
These are pretty discreet, easy to use, never had a problem with them. I believe they are the successors to the 3005's. The 3005's have lasted years and I don't recall ever having an issue with them either. I would wager we have about 250+ of those. They then feed into an ipconfigure server. We actually use a different model in our auditorium but that one is mainly used for attendance.