I have not personally tried the tmpgenc - however on many of the other forums I read, especially the Canopus forums, all the pros rave about tmpgenc. They all claim it is the only encoder they will use now.
I plan on trying it on my next project a few weeks from now.
You can get TMPGEnc here. There's a free version, but you have to pay if you want MPEG-2 encoding. There's also a trial version so you can see whether it's worth it to you. It's good, but it's also slow!