I've been looking at third-party lenses (Tamron, Sigma etc) for my Nikon D5000, as I'm not keen on spending a load of money at this stage - I'm still only at the learning stage.
Do you lose anything by going with these third-party lenses - except perhaps the quality of the lens? e.g. Can you still get things like auto-focus and VR functionality - or would I need to stick with Nikkor lenses?