Skinner
Trakanon Raider
There are some limitations, but I don't remember exactly what they are. I know guild improvements "stay" on the server you build them on so if you have a fully upgraded guild and move it to a new server you'll have to upgrade everything again. You can /w and mail cross server, talk and join guilds from cross server, but I'm not sure what the grouping limitations are. I know that if you're in an overflow server you can have people /join on you or /invite others and they can join you and even run instances within that overflow, but I'm not sure if they can "follow" you from zone to zone and group with you being from different servers if you're not in one. You also can't receive guild buffs, see guild upgrades, or accumulate guild influence for a guild that is not located on the same server as you. If you change servers, you lose the accumulated WvW bonuses for the week from your previous server and you're blocked from benefiting from your new server for 1-2 weeks (but they are useless anyway).
The guesting feature was supposed to allow you to visit other servers to play with other people but it hasn't been implemented yet and there is still no eta.
The guesting feature was supposed to allow you to visit other servers to play with other people but it hasn't been implemented yet and there is still no eta.