I have found quite a bit success with TDNAM domain names. I had picked up a domain name at TDNAM for approximately $100 that I have just completed escrow on for $3000. Held the domain name for about 6-7 months.
Now, are there gems on TDNAM? Yes. You have to know what to look for and what situations to avoid. My recommendations are to search for domain names and if you think you find one, wait until the last few possible moments to place a bid. The second you make a bid, you "highlight" that domain name for other people. You'll instantly attract much more attention and may get into a bidding war if you do it too soon.
Be advised, there are several large buyers on TDNAM and on some of the top names, your going to have trouble wrestling away at a reasonable price. Good luck!