My ARM platforms are largely M4 based with NXP LPC43xx and various TI TM4C12xx and CC3200 offerings, and I am amazed there are not more bugs in the NXP peripherals due to their sheer complexity. Their State Configurable Timer for example is tortuous to configure. The same applies to high speed ADC in the LPC4370. Of course, as with most vendors, they try to wrap up the peripherals in cotton wool with an API... which rather inconveniently doesn't cover all bases, so you frequently have to directly hack the peripheral registers anyway. Basically, always keep some of your own boilerplate code around for re-use or you'll be reinventing the wheel every time youmwant to,use a peripheral.
After moving from PIC32MZ about ten months ago, I found the NXP devices to be mature and refreshingly relatively bug free albeit with often outrageously complicated peripherals.
The compile/program/debug cycle is slow though on NXP. I use the LPC Link2 with LPCxpresso, I am not sure if this is just LPCxpresso or the debugger tool itself, or both, but TI's Code Composer Studio is faster in this respect. LPCxpresso seems to be dependant on a bunch of loosely coupled software components like Redlink Server which I am sure is part of the reason. The bolt on environment that NXP have added to Eclipse is a bit "how you doin'" in that if you inadvertently don't use their home made wizards, you open yourself up to a whole world of pain.
I also find the LPCxpresso debug environment to be flakey, although some of that is user error, if you forget to stop debugging a core before trying to debug again, it can be trying to recover yourself. You just train yourself not to push the wrong buttons monkey style. Such are the joys of supporting multi core simultaneous debugging I suppose. It also seems to take time to "make" even a simple blinky even when it's already up to date. However LPCxpresso does work, I can't ever remember it crashing on me (apart from trying to recover a debugger connection), but inevitably as soon as you move beyond blinky and start getting under the hood it is quite hard going. But that's the same for any MCU.