Epic Community Manager SixOkay has published a list of known problems for Gears of War 2 on the official Epic forums, including acknowledgement for the slow matchmaking issues that many gamers have been experiencing.
"Please help us out. If you see someone posting or asking about something on this list, direct them to this thread. Also, if your issue isn't on this list, please add it in this thread. It'll help everyone stay organized, and help us track things down MUCH faster."