If they occur at all, rubber-banding, lag, and inexplicable teleportation events dominate them. I'm no expert but that won't stop me from saying that P2P sucks big time.
With ED and a central server you might have even more problems. Helps if you know a little about networking but the basics is quite simple.
With P2P you are talking directly to the other client. With a central server you are both talking to the server, which adds latency and potentially extra bottlenecks.
To put it like as a real world analog, imagine you are sending messages to each other via courier. You live in London, the other person lives in Glasgow, and the courier office is in Cardiff. With direct delivery your courier can go straight up the M1, then west on the M62, then north again following the M6 and then finally the M74 to Glasgow.
With a centralized server in the same scenario youre heading west from london on the M4 to Cardiff, then handing the message over to a new courier, who then backtracks on the M4 goes north with it on the M5 and then getting on the M6 near Birmigham to follow the previous route.
Now, if there was a traffic jam on the M4, the central server mode would suffer even worse, whereas the P2P model wouldn't. Conversely, if there was a traffic jam on the lower part on the M1, in this situation the central server would do better (for this scenario). And if the upper part of the M6 was busy, then both models will have problems.
Now just imagine you have two people in London with a central server model... both sending messages to Cardiff when they could be passing to each other just down the street.
So, in terms of latency, P2P is probably the better choice.
What may be the problem for some people is router issues which for some reason are not handling the direct connections well (traffic jams).
