2) I'd like the possibility to rewind the game even once one team has surrendered. I often want to watch the game to conclusion then go back and rewatch critical portions; right now that isn't possible.
3) A spectator search function. This would be extremely useful. For example, if I'm trying to learn Kayle, the ability to search games with Kayle in them would be very nice. If I'm trying to see how 1600 ELO players play -- 2500 may be so far ahead of me that I don't necessarily learn much, while 1200 is too low -- a search by ELO level would be appreciated. This would also help find extremely high elo players who you know are playing but aren't technically in the featured games list.
4) Lastly, the ability to watch from a players actual perspective, to see how he manages his screen real estate. Seeing what they look at and when is very useful.