CB, you are not alone. I was hung up on 58" as ideal (for me) for years. I hunt in thick stuff, blinds and tree stands, and just felt longer bows were too much trouble. Besides, short bows have been all the rage for a couple of years.
I had a 64" recurve pass through my hands a few years back that I shot extremely well. I sold it because of the length. I knew then, as I do now, that I shot it better, in part, because of the length; but I needed to continue on my quest for the best compact bow.
Needless to say, I've had some great 56-60" bows over the years but my accuracy/consistency would vary. More recently, I started taking a look at longer bows, mild R/D bows to be exact. Since that time I have experienced the same phenomenon you have.
Not only is my accuracy/consistency improved, I'm also noticeably more comfortable shooting higher weight and for much longer periods of time. No more shoulder aching or arthritis complications as I've previously had after long shooting sessions. I have sophmorically attributed this to a smoother draw/force curve - although I have no proof of that.
Whatever it is, I'm sold on it. I've just about completely converted to the longer-bow camp. There may be no scientifically definable difference but my shoulders FEEL it. I've also had to eat a little crow and admit that the longer bows are not as much of an inconvienience in the woods as I once thought. And ... these mild R/D bows are sooo quiet while being surprisingly quick. For me it is the way to go.
I hope I can remember this the next time I see a short temptation in the classifieds.