Weighted dips are a proven exercise for upper body mass. Not a theory at all to people with lifting experience. With different hand positions, a more selective focus on certain muscles can be achieved: triceps, lower pec's, anterior delts, ect. Like any other exercise, dip's (weighted or not) may not be for everyone. Joint, liagament, etc, problems seem to be more present in heavy benchers than people who use weighted dips, from what I've experienced over the years. As I suggested before, warm-up and do not go to any extreme stretch at the bottom position. What you feel comfortable with should be find.
When using a 'V' dipping bar, for example, more opportunity is given to try wider and different hand placings. The pec's and delt tie-in seems to be brought out more. In any case the weighted dip is a superior movement. If it's not for you, than it's not for you. Do any exercise you like. Don't think that you have to do a certain exercise because some people recommend it.
Extended information for The Pumpster, who seems to need it very badly: We have a 'V' dipping bar in the garage gym, which I have used in the past. The pec's (lower) were getting to big for my purpose. (not a real big fan of large pec's on a man. On a women, that's another story). He did not acknowledge it, but I hope he noticed the site's (just a couple, more out there) that featured 'V' dipping bar's. As The Pumpster thinks that these dipping bars are a myth, I hope this helps. He challenged me to find a source for the 'V' bar. I felt it my duty to help and inform him due to his lack of understanding of BB'ing and equipment. Good luck.