I'm undecided about jigsaws - although they are fun to do, I always feel a bit guilty, as if I should be doing something more productive.
At least with other spare time hobbies, when you are reading, or going for a walk, or baking, or knitting, or doing a crossword - or even watching the tele - you get something out the other end, or it is generally good for you in some way.
Jigsaws - well, I mean, once you've spent some hours, over a number of days putting all those little pieces together, all you do is break it all up again! It hardly adds to your life - you might as well have not bothered and just die a bit earlier instead.
But that's a bit harsh, really - I think that there is a place for doing something just for the sake of doing it, it's fairly mindless, but at the end of the day, it's enjoyable, and you do get some sense of satisfaction at the other end.
I wish someone would tell that to my conscience, though, as it points out the pile of ironing or a dozen other things that I 'should' do instead...