Comcast has remapped [almost] all HD channels into the 1000 range, though they also still exist at their old locations (for example, FXHD is at 224 and 1207). HD channels are now in logical clusters (i.e., all the sports channels are in one block, the family channels in another, etc), making it easier to find things, and I think they're harmonizing the local lineups to be consistent nationwide. Locals are in the 1000-1010 range, with the last digit matching the OTA address: WLAJ 53 is 1003, WLNS 6 is 1006, WSYM 47 is 1007, and WHTV 18 is 1008. WILX 10 is missing, with 1010 being a dupe of 1006 (WLNS), but I'm assuming that's a bug that will be sorted out soon.
If you had a channel in your favorites, it automatically added the re-mapped version, so each HD favorite is now in your list twice (which is a but confusing).
It doesn't look like they've added any new channels.
Update: 1010 is now WILX.
Edited by pierceive - 4/25/13 at 6:02pm