Lady T, I started running early last year (for the first time in my life, except for those horrible middle school years when I was forced to take phys ed instead of dance). I started at the age of 45, and trust me when I say that anyone who knows me well was completely baffled and surprised that I decided to try it.
My motivation was a personal challenge -- to run the majority of 13.1 miles in a half marathon, as I raised funds for the Leukemia & Lymphoma Society with Team In Training. I started training in February for a race in June, and when I started, I could run for 1-2 minutes, walk for a minute or two, and then run again. Since then I've run another half, as well as a couple of 10Ks, 5Ks, and metric half (8 miles). At my peak when I'm training, I can now run about 5-6 miles without walking (other than a couple of water stops). I'm not fast (I'm happy with an 11-min mile these days), but I do have endurance.
In the summer, when it's hot and humid here, I switch over to swimming more than running. I'm not a hot weather person -- I get overheated easily -- and having a pool in our backyard makes this easy.
I've also taken yoga classes on and off for over 15 years, but I must say that running has had more of an impact on my sense of bodily well-being than anything else in my life. I lost about 15 lbs and 1-2 dress sizes, but more importantly, I toned up and my blood pressure is great, whereas before it was a bit more borderline. Having lost both parents to heart disease, this is really important to me.
I'll probably never be model-thin, but I'm much more comfortable in my skin than I was in my pre-running days.