This seems pretty cool! But I'm surprised they're not getting attacked by Apple since they're reselling their product as something else? (so confused) I have a MBP w/R it's a nice laptop, making a tablet sounds cool xD
Think of it this way: they're not selling products, they're selling service (modding rMBPs). Even if you buy a new one from them instead of sending them your own to get modded, you still buy it "from" Apple, i.e. the money that should go to Apple still goes to Apple.
I didn't even read all the specifics yet (just some) and it sounds like a fabulous concept. Not that I can afford it or anything... But I can certainly imagine that it will be a great tool for digital artists of any genre.