I can't see what enjoyment people get out of it at all. Lifting stuff and running/cycling/rowing on the spot just isn't fun to me in the slightest. I've been going twice a week and shall persevere, but grudge it.
Playing sport on the other hand is great fun.
Sport is definitely the most fun, but there is something immencely satisfying from maintaining a strict lifestyle and seeing yourself improve... especially with pull-ups (which are, you know, the hardest thing ever).