My general impressions with a wired cable connection, XBox 360 and all ports properly forwarded...
1 Bar: Unplayable and I don't expect it to be.
2 Bars: 50/50 dice roll. Sometimes the connection can be better than some 3 bars, other times it's quite delayed. I play a friend from Texas, he's wired, we ping 100-120 ms to each other and get 2 bars but it's very smooth with very little input delay. Other 2 bars can be very laggy, though.
3 Bars: Generally good with little input delay, but capable of lagging if the other person is on wireless or for other mysterious reasons (latency, non-open ports?). For example another guy I play, we ping 60 ms to each other but ingame the delay is massive because of his wireless. As usual, wireless ruining games.
4 Bars: Never seen it, but I'm in eastern Canada and it might be that there aren't enough people from my region to see/experience it.
There are desyncing problems with the game, but I can't pinpoint the reason. Texas guy's internet is slightly unstable and wireless guy is, well, wireless. Either way they do happen and can cause the game to drop/time out when starting the next match. I've played many more people than these two. I will say that when the game is good, it's really good, the input delay is very negligable, but when it's bad it's quite bad... but because I don't know every setup for the people I play, I can't tell if it's the game, their wireless, improperly forwarded ports, congested network, etc.. It CAN be excellent, that's all I know.