Although it looks like the overall network performance is great (there is no LAG at all) a low-bandwidth/disconnected icon appears in front of the screen. Even when the battle goes back to lobby and starts again the icon re-appears. I'm testing from Chile but I have no problem playing online games like COD. (I have an 10 MB broadband conection)
At the moment the Beta is not running, but when it did many people were having the same issue.
Tank sent a message on the forum saying they turned off the disconnection icon a week or so ago, so I would be surprised if you are still noticing it.