First and foremost, it's the people, as Joe said at the outset. With the exception of a few threads mentioned by Seed, the discussions are always well-mannered (that's a lot more than you can say of many newsgroups out there).
Where else would you get to hear about Big Mick's Grandfather's house; I almost feel like I've been there after reading your description Mick. As for being or getting old, at 43 I'm just a pup I guess; but I think it's mainly between the ears.
It's for these reasons and too many more to put down in words that I like Mudcat threads.

Dave T