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).
Aside from the standard POSIX/Unix interface, another big difference
between NuttX and the very tiny RTOSs is that, like Linux/Unix, NuttX is
very console oriented. Certainly there are many NuttX embedded systems
that are field "headless", but most included a usb, serial, or telnet
console and a tiny bash-like shell if only during at least during
development. Of course name of the shell is the NuttShell (NSH) ;-)