Extremely easy to use with arduino IDE, works like a charm, you'll need some skill to solder to your pcb but hey, you have seen the pictures right? I used the 15x15 configuration that I obtained by sanding away the larger part of the board that was shipped to me, that operation didnt damage the chip and/or the connections integrity. Very satisfied!
Albert did a _really_ nice job designing the SAM 15 X 15 board, but it gets messy from there. The documentation is all over the place on his website. It's not obvious which libraries one needs to get the board up and running. He has one large zip file that has all the "needed" libraries in it but many of libraries are by other vendors, and doing a straight copy overwrites what my be important without knowing it until later on. It would be nice if he spent the time to put all the examples strewn around his website into an example folder. Doubly nice if he spent the time put all his libraries in order per Arduino spec. There's a reason I love Paul's work on the Teensy, but truth be told if Albert can get the doc/libraries for the SAM 15 X 15 in order it's hard to beat for the size.