1)If you/your players have scrollwheels on your mice you should be able to click in the player sidebar to then scroll down to get to the chatbox. (Severely annoying, especially if you don't have a scroll wheel. They're working on making this easier)
3) Are you trying to add characters while people are already in the game? The character tabs seem to only refresh when you first join the room, so make sure all characters have requested to join and been approved before game time to avoid the issue. (The ability to update sheets while in game is in the queue, so this may be solved as well.)
4) I like this. Reminds me of the features in Elluminate (a webconferencing/classroom software). It could be a button next to your webcam picture that puts a raised hand or something. A related fix, thoughts on allowing the GM to mute everyone else to ensure s/he is being heard? (I know we can mute people for ourselves, but i mean for everyone!)
5) I haven't had this problem with my group, maybe your players need to adj their mic sensitivities. Technically this functionality does exist already, you can have your players mute their own mics by clicking the little button in the webcam picture just as they can toggle their video on/off.
6) The imported picture list mentioned in another thread would really help with this issue I think. (mainly since i've been playing with maptools again)
2/7) Lag hasn't been an issue with my group, but it gets really annoying how sometimes people have to leave and rejoin because one or two others can no longer see/hear them.