I've got 3 genuine concerns with Elo. E.g. things that influence the quality of match making.
New players
New players are put in with an average Elo. They will descend down but on their way down they'll run into allot of people with average Elo that are annoyed by the fact they'll lose what would otherwise have been a close game due to a new player on their team.
There are several solutions for this such as provisional ratings and accelerated changes for the first X games.
Old players, new mechs
A new mech is nowhere near as good as one with all the upgrades. By starting a new mech you'll handicap yourself and your team.
There are several solutions proposed for this such as using battle value or Elo for chassis + weapons + engines. If such a combo wins more it's obviously a better setup. This one will be hard to balance though.
Premades
People on Teamspeak have an advantage over normal players. They don't have this advantage when they play solo. In the long run Elo will find an appropriate rank for players who do either. If they do both however their Elo value is always wrong.
As such when players join a premade their Elo should go up a bit. PGI should have enough data to see how much more likely a premade is to win and adjust the Elo of a premade accordingly.
Edited by Hauser, 02 May 2013 - 04:59 AM.