I really tried to get on with the stock bar - rotating it fore/aft. I always somehow ended up with that stabbing in between the shoulder blades pain, like so many others describe. I found that when I gripped the bars with just my fingertips, it seemed to be more comfortable. A more bolt upright position seems to take the strain from the upper/mid back.
I tried an MSR Profile, carbon steel bar in the ATV High bend - got it on Amazon with a gift certificate for about $28. I really didn't feel like spending a bunch, just to test out a theory I wanted to test. It's an inexpensive steel bar, so it won't impress the anodized+oversized crowd! The bar doesn't have as much backsweep as the stocker, but it makes up for it with about 1.5" of additional height, so you can angle it back towards you to the sweet spot. I've always like a lot of backsweep, but surprisingly, I don't miss it at all - the more upright position seems to not require much backsweep for wrist angle comfort. This bar will require you to reroute your control wires/cables a bit, since this bar is pretty much as far as you can go without getting control wiring extenders (eastern beaver stuff) or new hydro hoses for the brakes, as well as dremeling off the control pods handlebar plastic locator pins.
Anyway - I love the new "laid back" riding position. It's actually much more dirt bikey of a riding position and is emminently more comfortable. A side benefit I'd not even considered is that since I'm sitting more upright, my Rick Mayer custom seat is incredibly comfy now - my nutz are no longer crowded between the seat front and my riding gear (I'm not a fattie, but there previously wasn't really a friendly place for "the boys" to kick back and relax while riding!] Now there is, and my back is happy as well.
I think you'll be surprised too how such a small change of angle and height can transform your ride perceptions. I get a laugh when I look down while riding and think "What a ridiculously gigantic dirt bike I'm riding - HA!