What aspect(s) in particular?
(Sorry, I had a quick look through the datasheet and didn't actually spot anything particularly stand-out that caught my attention, but perhaps I missed something.)
For M0-class devices I'm quite impressed with the NXP "switch matrix" for IO pin function configuration.Just such a cool and clever (and even useful!) feature. I've been playing with some LPC810 8-pin DIPs, looking at them as alternative to ATtiny85s for some applications.
Unfortunately, NXP only offer one other LPC in a DIP package, the LPC1114, which is nice, but only offers 32KB flash and 4KB ram, so apart from being faster (50MHz), doesn't offer much more than a 328-class device, really. Otherwise I'd be all over it.
The free LPCXpresso programming environment is decent enough, too, although a bit too "Eclipsy" for my taste (which is not surprising since the code base is derived from Eclipse, apparently.)
Moving up the ARM foodchain a bit I'm really impressed with what Paul Stoffregen has done with his latest Teensy 3.1 offering. Even 5V tolerant digital IO pins! Just too much bang for buck. It almost hurts to read the datasheet. 