Thanks for the feedback so far. I'm currently working on the issues you all brought up. Some quick answers:
The problem with the add-on not working after opening a new file is a problem that affects all add-ons that change the keymap. I'm talking with some other developers what the reason for this is, and how we can hopefully change it.
At the moment the workaround is to disable and re-enable the add-on.
Richard Marklew: thanks for the video. The problem you experienced is that blender's default functionality is to fill the end faces. The script won't do anything if blender already changed the mesh (this is a security, because otherwise default functionality could disappear). I'll add an option to the script, so you can override the default behaviour.
sketcha: strange that you can't enable the script. Are you using the official Blender 2.54 build (rev 31878)? Does any error or warning show up in the console (on Windows that's the dos-like box that opens alongside Blender)
Michael W: no, it doesn't loft yet. I'll have to think of a way to detect which loops need to be connected to each other, though I've just tested it in Blender 2.4x and it seems that the old function could be easily fooled.
I'll add the loft-function on my todo-list after bugfixing.
zeauro: I've just tried and after a few tries it did indeed go wrong. I'll investigate further.