I haven't used it personally but I've seen reviews that complained of bad latency, and doesn't work with some apps.
EDIT: After checking it out on their site, it looks pretty cool, if it really is compatible.
I've considered the line6 unit as it it quite "cheap", well, compares to other 30pin interface.
But just as Rip, I've not seen many reviews and it was not clear how compatible is this device.

