Do you guys put any trust in the claims made about vitamin and other dietary supplements?

for example, has anyone had a positive experience using chondroitin and/or glucosamine to alleviate joint pain? just as i started taking them to alleviate knee issues i re-injured my knee and so have no idea if taking them has had a positive effect or not.

this is a general question about supplements and the issues supporters claim they alleviate so anyone with comments about supplements other than those i mentioned are welcomed.

what have your experiences with supplements been? what would you wholeheartedly recommend or care to debunk in no uncertain terms?