I have an 8300HD at the beach and just upgraded two others to Tivo HD XL with M-Card in each. Install went well on both and great to have Tivo. As soon as the Tuning Adapter is available, I will get rid of the last 8300HD.
Tivo is fully functional and programable over the net. The 8300HD is barely usable. I had to have two hooked up to one TV to make sure I got games recorded and I can not count how many times I have been watching a game while still in progress and had the feed jump to live and ruin the ending of the game.
My opinion is Directv Tivo first, TWC with Tivo HD second, Directv HR22 third and TWC 8300HD a distant fourth. Can not wait for MPEG4 D* tivo.