Re: Middle aged Newbie
I'm 43, been training for about 3 years, and find that gentle falls and rolls are good for staving off backaches. Previously I had recurrent back problems and had to do daily exercises to fend them off; now I'm fine, though I have to go back to the exercises if I stop doing aikido for more than a few days.
I train in a style which does not emphasize high falls, and it's been very positive for me. Not only do the stretches and falls help keep my back limber, but my teachers insist on good posture, which is beginning to carry over into the rest of my life.
It's a good idea to visit a dojo before joining it. You can see what the falling style of the school is, and how accomodating they are of older students or ones with physical limitations. I have trained in a few places which were too physically demanding for me, but there are many dojo which are excellent with older students. Which style you choose is not as important as the individual dojo (for example, there are two Ki Society dojo in my home town, but one is much gentler than the other).
Good luck, and have fun! I found learning to fall initially quite challenging, but now it's tremendously fun.