A lot of people are having a similar issue. The forum moderator posted saying they were working on it.
I wouldn't mind the wait time too much if they gave me something to do in the game besides twiddle my thumbs. Mayhaps a training screen. Or like how it works with Desmond/Ezio when they wait to load, in that they can still move and attack.
I would prefer something as simple as being able to check the customize menu or look at the previous game stats, considering the time it takes to get a game started everyone usually instantly rematch's and doesn't bother to look.
Trying to get into a multi mode. No joy server looking for a session, i part ex`d a really good game for AC:B seeing i have the other two and was really looking forward to this online. WTF UBIsoft sort this issue out already, if you have released the game then surely everything should be in place and we dont have to wait for a "fix" is this another case of get the game out before xmas rush?