Live chess features lag bars that are intended to indicate quality of connection. They have a green/yellow/red code. The lag bars are located to the right of each opponent's name on the live board.
My experience is that sometimes the lag bars are a little pessimistic in their prediction of actual lag during the game.
I just finished a bullet (1 0) game that lasted almost 15 minutes. My opponent took between 7 and 15 seconds for each more on my computer. Of course this is because his connection is very poor, but it's hard for me to react very quickly. I know that there was a similar delay on his computer as well so it's not unequal or unfair per se, but:
So there should be a way of identifying opponents with bad connections or perhaps the option of aborting if one's opponent has a very large lag.
I don't know if this has been suggested before. If so, please don't hesitate to tell me off.