In reply to Inhambane:
> im definitely not going for style points, i was just wondering if technique wise it was bad that im somehow taking a short cut which may impact future climbing
As far as knees go, if you're 'standing' on a knee then you have no extension left. If you were standing on a foot instead, then you'd have a good three feet of extension available by straightening your leg. Consequently, using a knee can have consequences that need to be considered - namely how are you going to get off that knee again. If you're at the top of the crag, no problem; elsewhere, perhaps not. Usually less elegant than a foot, but not necessarily.
Knees are almost de rigeur for mentally hard steep stuff, where a knee bar may provide a rest, but not in normal usage.
Winter climbing - be careful what you kneel on: - rocky thing, OK. Ice, to end in tears.
Elbows - who cares.