Two things I've noticed.
1. Multiple people can pick the same champion. I've seen this happen and then arguing over who gets what role, despite what the roles were picked by the system. I had a Top, Me (Support), and the Jungle all pick Nami. Yeah. Yeah. This shouldn't be allowable, one person per champion.
2. When you're thrown out of queue, the little chat goes all the way to the top of the chat log. It should stay at the bottom instead of scrolling all the way up.
1. If a Champion is selected, it's not selectable by the other teammates.
2. Make it so the last line of chat is the one displayed, not the first.