A dev manager I work with insists that one of the best indicators, along with all the usual things you try to suss out about a software development candidate is whether or not he does any software development in his spare time. Not everyone who's good does, but there's a good correlation between people who would be good at writing software, and people who do it for fun.

So I would take writing software for fun as a plus, but would not take not writing software for fun as a minus.