A few days ago, Vsevolod Klementjev (KleMiX) released iTileMaps for iPad. Since quite a few of Tiled users are developing for iOS, this will be of interest to some of you.
iTileMaps allows you to view and edit your tile maps on your iPad. Even though it's just the initial release, it already supports most features of the TMX map format, including editing of object layers and properties (see its website for a list of features as well as current limitations).
The developer allowed me to try it out, and the main thing I noticed is that it runs very smooth. Also the interface looks pretty good. It's certainly not more efficient than editing the maps in Tiled (yet), but I think it has a good potential once there has been more time to learn what works and what doesn't for a touch based tile map editor.
If you find this interesting, don't hesitate to support KleMiX by getting your copy. He's also very open to feedback (just like me), so let him know how you think he could improve iTileMaps!