I agree they should offer STL models for people who want to do the slicing themselves, but I do like the idea of providing presliced models that are tuned/tested for popular printers.

EDIT: "We guarantee that if your print fails, you will be given as many opportunities as needed to re-print and get it perfect. L2L allows us to track the completion of every print."

So I guess the purpose of a proprietary format is to restrict the number of times you can print a file? That's not going to work very well when you're interfacing with open source printers. I imagine it's trivial to slurp the gcode off the serial connection to the printer.