This is for 1.2 features explicitly mentioned by the developers.
Here is what I got so far.
Various balance changes (See trem.tjw.org for starters)
Voice-chat menus
New UI features
New HUD
Unlagged, like it or not
New maps
Revised trigger system, including trigger_equipment and func_train.
New building system (Deconstruction)
New models, including the marine and weapons (Possibly Choppers).
New sounds
Post other confirmed features so I can add it to the list.
Feel free to also post and rants and raves about the above, like what you're looking forward too, and what you aren't...[/list]