For me, a release is an absolute necessity on any bow that is less than 8" longer than my draw length, or with a bow that is more than 70% letoff.
I've got a couple of older bows that measure 46 and 48" long, one is 50% and the other is 65%. Based on my average field archery scores, I can shoot both those bows MORE accurately with fingers than I can my 36", 75% bow with release. But then, I only started using a release 3 years ago and I've shot fingers coming up on 47 years this April.
I still haven't gotten over the feeling that a release disconnects me from the act of shooting the bow. I like having my fingers on the string. I feel like it gives me total control over the shot and that gives me a lot more confidence in my shooting.
One reason the pro shops recommend starting out with a release: They get more profit from selling releases than they get from selling tabs. <img src=icon_smile_wink.gif border=0 align=middle>
(No offense meant, Len, Pinwheel, et al. Just jerking your chain.

)