I've got one of the NXP mbed boards, and it's an interesting piece of hardware, however, the current mbed toolchain is kind of ridiculous. In order to use the more interesting features, you're pretty much required to use their web-based IDE, and forego a lot of the nice features of, say, eclipse. Also, I have issues with certain decisions they've made, like having floating point only libraries for PWM, which means you have to waste a lot of clocks, and code, just to make the lights work.

Then again, with AVRs, I'm using Atmel Studio a lot these days for similar reasons instead of the Arduino environment. The abstraction layers don't quite mesh with what I'm trying, which means writing I'm writing around the Arduino a lot more than I'm writing for the Arduino. Perhaps it's just time for getting back to basics with the lower level libraries.