Put me in the camp of enjoying HD over Showtime and HBO. I watched "Apocalypse Now Redux" last night and it was amazing! Certainly better than when I saw it in the theater, which could be due to any number of factors, bad print, bad projection, etc. If what I saw last night was "upconverted," then I'd eat my hat, if I had one.
I also love HBO-HD and I don't care about the aspect ratios. "Gladiator" was shown 16:9 and it was immeasurably improved from the theatrical version (although I'm told it was "open matte," which means that I saw the entire theatrical picture and more). I recently watched "Forrest Gump" in HD at 2.35:1 on HBO, so I guess they have used OAR as well as full screen in the past. Forrest Gump did not have 5.1 sound, so that was the tradeoff, I guess. The sound is less important to me, as you can tell from the choice of my equipment: very expensive Fujitsu 50" plasma and cheapy Boston Acoustics surround sound. I live in an apartment and I can't really turn up the volume, except maybe on Saturday afternoon.
My only complaint about HD: there isn't enough of it. I've seen all the HBO and Showtime movies, some of them, over and over. I'd like Time Warner cable to provide a Pay-Per-View station in HD, and they'd get my money. I'd also like ABC, PBS, and Fox, and Discovery, to come over my cable. September 11 took its toll on New York's HD market, and we are still waiting for solutions.