I absolutely love this thing! It's like an Arduino on steroids. Since the on board 32u4 uses the ISP interface, no bootloader necessary and fully compatible with Atmel Studio.
And lots cheaper than an Uno!
I love the mega328PB, although I really wish they made a PDIP variant.
One thing I learned the hard way...DON'T MESS WITH THE FUSE BITS!!! I'd forgotten that the 32u4 supplies CLKOUT to the PB and for some reason thought it had an on board crystal oscillator, thus I ended up bricking one after changing the oscillator fuse bits. No need to mess with them on this board. Worry about that in production.
Other than that this is an excellent development platform. No need for an external programmer or a bootloader plus you code it with the WinAVR compiler in Atmel Studio. Couldn't be better.