i was playing the other night with three friends, and there were way more than the normal issues...
black screen, countdown stopping at 1 second, gamertags being replaced or seeing them twice in lobby, etc. all of which required dashboarding.
then there was the placing of one teammate in a totally different match on the same map. we were in party chat. so we could still chat and see that we were not in the same game.
we also had the "cant connect to host" issue even though we were all open nat and in the same party chat...so obviously there wasnt an issue connecting to each other that way.
quite a few times we would be placed in a full room only to be moved to a room where only the three of us were there.
one player would be stuck at the loading screen showing the map while the rest of us were already playing.
host also dropped a few times, and the game lost connection instead of continuing with a new host.
for about an hour of being on live, i think we probably got 3 or 4 games that werent screwed up.
this was all in one night of play.