I don't know if more compression is happening yet. But I believe that according to FCC regulations, they must broadcast the local stations, including HD, without degrading the quality. So if they are further compressing, it would be on the other channels. I personally am looking forward to TBS-HD for baseball, SciFi-HD for Battlestar, and AMC-HD for the occasional movie and Mad Men. I want "less-compressed" HD, but I'd rather have HD-lite than no HD at all. And I would hope that in 2009, Comcast would eliminate all but the locals from their analog offerings and free up room for better quality HD.
And in my part of town, there's no FIOS option. But if there were, I'd consider it too.