I like the dial access system to the critical controls, and the shooting modes, rather than menu-buried access. It's also a good-looking machine as well. The built-in hotshoe is also a major plus.
That's a pretty awesome camera. I'm looking at the spec of the newer P7800.
It supports CLS, and the SU-800 which means it should work with my Yongnuo 622TX flash controller.
All that in a compact unit too.
The P7800 does 8fps too compared to the 1.3fps of the P7100.
Not bad for either in such a small system.