After reading this thread and listening to one if the HD techs explain battery maintenance issues at this months' HOG chapter meeting, I'll be getting/using a battery tender. As was said above, it's the best stung to do for a battery in a bike that may sit idle for days or a week or two at a time.
i use them on all my toys all the time, 8 years on my softie battery and 7 on 1 in my truck and car, they don't get driven much and can sit for weeks at a time.
I say yes, for me because I don't ride much during the week. If I do--it's on casual Fridays. I've found that when I don't use one on my lawn mower, it doesn't fair well either