Since when is 85% satisfying? If there's a 17-18% increase in downloads out there by simply using a slightly different API and memory technique (not being able to use weak references), then I'd say it's worth it.

According to my experience that's an understatement of the benefits of not supporting old OS versions (and the negatives of having to support them).

Interesting. I would love to hear more about your experience and that point of view. Do you have a blog?

I do but I've not blogged about iOS stuff really. You've got a couple things to consider. One of the big ones is maintainability going forward - old code & processes cost more to maintain and add to software entropy overall.