I'm ready to do this too, having come from using Cocos2d, which has a class for working with Tiled maps. I saw how it was done in the Platformer demo, which is basically he added static bodies to each tile that had a certain property, then made a resolve collisions function, which would check collisions between static and dynamic bodies, that he passed in the player's dynamic body in as a parameter.
What would be nice for me is to have the Tiled class return a tile and its properties by either passing in a row and column, or a Point, like a player position.
Even cooler would be a list of tiles/properties if I pass in a rectangle. This would give me all the tiles that are touching a player at a given frame.
I'm happy with the Tiled class so far, but I'm curious to see how other people are handling collisions without these helpful features.