My top ones are:
1. Decent matches with good match. I think MF's automatch did better, in my case.
2. Probably a requirement for 1), ranking, without a large daily decay.
3. A way to invite players to a game, with some control over who joins the table, like one could with the goko salvager extension, e.g. "twasa's 3p 3000+ vpoff". This mostly for players who enjoy games that have more than 2 players.