You, the pilot/player, will be given a performance rank. When launching, you will be in a team. Your team will be against another team. That team will have a player roughly in the same skill level as you. Basically, one of your enemies will be about as good as you (hopefully).
I see everyone claiming that this will help prevent stomps, and better yet, PUG stomps, and that's certainly true. But I don't think it will be the miracle cure people are expecting. At this point, its just speculation using all the facts that I know/understand.
If you are a medium mechwarrior, your skill level will be applied to other weight classes. Which means even though you are a medium pilot, someone roughly your same skill might be piloting a heavy, assault, or light, but they might also be a medium as well. So even though your skill levels are supposed to be similar (and on the basic level of being able to move and shoot they just might be) but at that point all equality is offset by the mech types. A medium against an assault, of similar skill, the assault should win, right? This result might actually help foster teamwork even more since the medium will most likely need help. That or the medium pilot might pick on someone their own size.
Stomps among only PUG players (PUGs vs. PUGs, and yes I believe these matches DO exist), without significant difference in teamwork competence, will most likely be gone.
Sync drops will probably be more difficult to achieve since pilots will have to be pitted against pilots of roughly the same skill. Basically, if one premade gets into a match, there's no telling if the enemy's pilot skills will match enough with the 2nd premade's pilot skills. It might, but it probably won't.
PUG stomps (premades vs. PUGS) probably won't stop as people claim. The PUGs might have a better chance since supposedly both teams will have roughly the same average skills, but you're still pitting people who have better communication, and coordination against those that don't. Maybe if premades were only pitted against premades of roughly the same average skill, it might be an even smaller issue, but as far as I understand, that's not the case.
I suppose an option for PUGs to have the "no premade button" will fix the pug stomp problem. That or making it so 4-mans are individually pitted against equal 4-mans, not as player vs. player, but group vs. group.
Also, I suppose 8-man will be salvaged by Phase 3.
Yes, I read the dev. posts on Matchmaking. If I misunderstood something, please enlighten me. If I forgot, or didn't know something, please inform me. If you have your own speculations, go ahead and share them. But let's be adults and respectful MechWarriors on this thread.

Edited by Coole, 10 January 2013 - 12:30 PM.