A little. :-) I've worked on a few commercial projects in recent years and way back I did SCADA and real time systems and been involved as a hobbyist for 15 or so years. I’m spoken at the Open Hardware Summit and given a number of IoT and MyNewt talks at various conferences, and run basic Arduino courses. I organise the IoT meetup here in Sydney. One of the reasons I put my hand up to mentor this project, but I’ve never used NuttX.
You will find it is a little "beefier" than Mynewt or Arduino. It is a full Linux compatible RTOS (but much, much smaller than LInux). So working with NuttX is a little more like working with Linux than with other really tiny RTOSs. Somewhere in between. NuttX apps are definitely like Linux apps. That is a consequence of the portable POSIX OS interface. Most Linux code can be made run on NuttX (but often with having to bring some less-than-standard Linux definitions, and dealing with all of the libraries used in Linux development).
