When playing Madden 08 online, i find some games seem to run ok and other are just painfully laggy. Most of the time you can tell if someone is laggin' by the team selection page.
When you are choosing your team, check out how much lag there is between the time up switch from one team to the next. If it seems to hang up between teams(or take too long), you know that your opponent has a terrible connection. Try that out. Seems to work for me. That's what I do.