Hopefully two non-controversial ideas.
The first would be to add replay speeds between 1x and 2x. Audio commentaries tend to be in 1x speed and I always find that a bit slow, so hopefully if there is a slightly faster speed some people could use that one.
Second is that if you would ctrl+l-click/double-l-click on mineral patches you would select all of them and there would be some attribute: total minerals. This so that if you're watching a replay you can easily spot how much damage(delay) harass has caused, or how the more offensive style of the zerg player worked out, and so on.