Speaking of myself, yes NAnt is still in use. I have a standard build script that I can easily add to any new project. I do this for any new code that I plan to keep for a while.
NAnt is mature and is widely used in many projects. Most of its appeal is extensibility through custom tasks.
The project seems to have stalled, but apparently it is still alive and kick, according to this post . There is some talk of a roadmap for the future, as well as a new version.
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