>>872553>altimeter/compass reliableIf you calibrate them often (weekly), they're decent.
GPS elevation is fine for most uses.
Compass ... unnecessary fluff IMO. Carry a cheap one, they're a lot more useful than the electronic one in the receiver. That one's irrelevant when you start moving anyways.
Take a few steps in the direction you want to shoot, and the GPS will update your heading. When you're stopped, it'll wander around.