With Umbra I think it'll be a huge difference from SW:tor and WoW becouse the things you've to load is just so much less. And they don't have an combat-log like WoW which has to get everything (donno if GW2 even have a combat log, I don't think it has tbh...), i.e. the lag will be less of a pain.
What I pray for is that we get some epic battles in WvWvW, like huge collisions. Even though I enjoy the idea of having a sneaky tactic like destroying caravans, taking over mines and all that for getting advantages I still want some huge fights. A little bit of that epic feeling you get by just watching LotR
If WvWvW just give me 1/3 of that feeling I'll be God damn happy.
I believe in A-net, they'll pull this off!