Actually they are adding a pause and a fast forward. I posted on this some time back. There was the whole discussion on why there couldn't be a rewind. Some of you may remember this.
The reason for this is because replays aren't a recording of a game. They're a file that remembers mouse clicks, unit movements, etc, and then uses the actual map to play the replay on.
Because of this you must have the map installed for the replay that you're trying to watch. This sometimes causes problems for people that download replays for maps that they don't have.
When the pause and fast forward feature will be implemented I'm not sure about.
Production Support Technician
Command & Conquer Generals