I did some time back. It is not all Gravy. At the time the only C Compiler was not very efficient. There is another one now.
The Digital Blocks worked very well. The Analog Worked, but was low quality ( offsets, drift, noise). The on the fly reconfiguration was nice, but I found you had to due to limited resources. The Pin Muxes are limited, so you can move pins, but not any pin anywhere ( Like siLabs?). With the Analog on it uses a lot of power. The data sheet at the time made you work very hard to find out how much. The core is a very generic 8 bitter. There are no bit instructions. At the time RAM and ROM where limited, They may have bigger parts now?

I can be a good part for some applications, But I found it over marketed.