Guild Wars 2

Players do a variety of things on this game.
Some PvP, some do Fractals, some Raid.

Being such a versatile game, it is important for a player to be diverse.
They often switch builds to meet the specific challenges they face.

That being said, it would be very convenient for a player to be able to switch builds on the fly. The original GW1 used client side save files which contained user created custom bars.

Similarly GW2 needs a way to save build configurations for players.
This has been mentioned before.
However, now that the game emphasizes raiding more, we need this feature now more than ever.

A simple example is playing PVE as a Ranger in a Marksman/Skirmish build setup for dps and exploration, then quickly changing to a healing Druid build so they can run Spirit Vale.

This has obvious advantages.
1) It saves the player from having to manually change each and every utility in their skill bar.

2) It saves the player from having to manually change the build in the specialization sections. (which sometimes they forget exactly the way it was supposed to be set)

3) It adds a new advantage. If it was stored as a file, players could share their builds with others. Simply by placing a config file into a folder on GW2 you could load a metabattle build on the fly. Think about how wonderful this would be!