I play many turned based strategy games with friends of mine and we always bicker back and forth about who takes the longest. I know *I* don't take long but boy do my buddies take FOREVER.
So I did a test by manually keeping turn time on a sheet of paper and when everyone ended their turn I averaged them. Low and behold, I was actually one of the slowest.
Anyway, what would be nice in a multiplayer game would be an average turn time next to each person's name who is playing the game. Simple code and I'm sure it's an easy addition to the UI. But having it IN YOUR FACE will make for many happier multiplayer games 
We don't play with a max turn timer as, well we all have families and interruptions. As long as we notify each other, we're good. It's the ones that think they are not slow who are the problem (myself included).
Thanks!