I mentioned in my initial impressions of the game that fast travel should be a necessity, but I'd like to push that idea a little further.
One question that comes to mind, do sub games really need to give players the constant run around? Themepark games like WoW and Rift seem to be following the trend of streamlining the quest experience into the monotony of going from hub to hub with very little backtracking, having such linear questing requires a straightforward flow in traversing the zone so as not to annoy the player. Could fast travel be a feature to break up the linearity and allow quests to at least expand across a zone if not the world? And that's just questing, Rift's invasions are zone-wide and thus fast travel would be a boon.
The only counter-argument that seems to ever get thrown-up is that it diminishes the feeling of the world, which I always find ridiculous when it's the linear structure of questing and the static nature of the zones that are the biggest culprits. Players could always imagine that whenever they fast travel, it's like whenever a journey is described by a single sentence in a narrative, and nothing eventful occurred, the end.
The simplest solution for Rift, is clicking on the round symbols that are already on the map and instantly travelling to that hub. The cost should be a planar charge. On a sidenote, I had the same three planar charges from the time I landed in Freemarch until I was level 42, only recently did I buy the wardstone upgrade power and the other power that boosts your character against planar creatures, and found them useful enough to start spending planar charges on. If planar charges could be spent on fast travel as well, then these powers might be neglected. Storing up to 5 planar charges might be the solution, the planar charge consumable that can be bought for 500 planarite is a little on the expensive side for low levels. Some other restrictions to fast travel could be to prevent it if the ward stone is destroyed, on the other hand maybe allow free travel when the wardstone is contested. In relation to GW2 should they allow their fast travel for karma only, thus tying fast travel to their events system, rather than the easier to acquire gold?
That's the basic idea, to be a big idea, there should be an additional feature to go along with the fast travel system, a flare that creates a fast travel point that could be used by anyone on the user's faction. The flare would create a focus point, the first person to use it would get charged 1 planar charge and the person using the flare would be charged 1 planar charge as well, the port would then remain for a few minutes and could be used by anyone else for the cost of a planar charge. It could be limited to only being used in proximity to a rift, foothold or an invasion boss, on the other hand if you were using it for a group quest then the players are down a planar charge, and would have to find a rift to replenish the charges some other time.
I really like that it could lend some sociability to a system, even if it's just to signal that you are going to work on a rift, and nearby players see the ping even if they don't choose to fast travel, they could either travel by foot or just be content in the knowledge that other players are nearby working on the content.