We want to get one of these for my mil, although she doesn't want it quite yet. My dh did some calling, and they sound pretty good.
Personally, having recently fallen on a hiking path and suffered the relatively minor consequences of that, I would definitely get a stair lift for the situation you describe. It's that old ounce of prevention......
p.s. I should add that I've fallen several times while walking in the last few years; the most recent one was just the worst. That decided me to start working on my balance and strength. Got a Wii and would recommend that for working on balance! Some of the other Wii games seem to be strengthening my legs too. I think that is an all-around great purchase for people getting up in years, although you do have to actually *use* it regularly to benefit. (We know several couples who have one but don't use it.)