I started running about 20 years ago, when I started putting on the poundage. The first couple of months were murder, but I kept it up. I had no real interest in running races, but my neighbour, who is really into it convinced me to give it a shot. It was a lot of fun and we're planning on doing another one soon.
I've been quite fortunate with my knees, which don't bother me whatsoever. Even when I was carrying a few extra pounds, it wasn't an excessive amount, so there wasn't that much extra stress on my joints. Plus, when I transitioned to the VFF's and a forefoot strike, I believe it reduced much of the impact force from my joints. It took a while to strengthen my calves and Achilles tendons, but I have no regrets. Plus, I'm at an age where I don't really care how I look when I run.
I'll be looking into a more structured running program so that I'll be able to reduce my times.