Public Game Matching System

[:1]It seems to be designed around matching players based upon their progression through the game. That's great, but there are two factors that the system must account for otherwise it will be a failure.
1) Twink v. non-twink. Twinked characters ruin the game experience of non-twinked characters because they are always disproportionately stronger than the enemies. They tend to hog all the action and put off non-twinked characters.
2) Pacing. Some players like to take their time and clear out every nook and cranny in the game. Others like to beeline it to the next area as fast as possible, only killing along their path or skipping enemies entirely. Neither likes to play with the other.
If players are consistently getting matched up with players they aren't compatible with, they will stop using the feature entirely. This is the only system for players to form parties with anyone in the region other than their friends. If it isn't successful, then a player's ability to network is going to be severely hampered. The good news is that it should be fairly easy to account for these factors automatically (as opposed to players having to rate themselves in these areas as part of the matching system).
The AH already has a feature that essentially measures a character's gear. Blizzard can just use the same principle when searching for players to make sure that only players with equivalent gear are matched. That way, regardless of how a player got their gear (twinked, purchased, lucky drops), they will be matched with players of equivalent power; no one outclasses anyone else.
The game can also measure a player's pace by tracking the amount of time a character has played and the amount of time they spend in each area. It can average those figures to match players based on the pace at which they play the game.