Dental lab experience = money!
seriously, its more useful than shadowing..doing build-ups and pontics and all that stuff will give you an edge on all the other dental students in your class. you do so much lab work in dental school from what ive heard, so the more exposure the better. I think the experience is unique..i haven't heard of anyone with thorough lab experience before, so that's awesome. We dont have an in-house lab in my office, so i just do minor lab work like welding seagull cleats, TPA attachments, bonded lingual retainers etc..so i would have mad respect for the stuff you do..moreso than someone that just follows a dentist around and watches them do things. keep it up.
ps..if dentistry doesnt work out, im definitely going into Lab work..i just learned today that my office alone sent one of our lab guys $10,000 worth of work (after taxes) for the month of july..and the overhead costs are pretty low.