It's a totally legitimate operation and good service from what I hear. I have never used it to rent points from since I already have DVC, but I have talked to him about renting points out. The only negative, as opposed to using the DVC boards here, is that you will not have any room for negotiation with him - I believe the standard point fee is $15. per point; maybe higher for holidays. These points are not actually his, but rather DVCers that need to unload or rent out their points for whatever reason. He is basically the middle man who takes care of all the hassle for both sides.
I would have absolutely no concern with using him - he has been around for a long time and appears to have a good reputation. Hope this helps everyone!