Aye, Joann's Kona is the real deal, assuming a sloppy storekeeper hasn't wound the wrong fabric onto the wrong bolt. I have (literally) put samples under a microscope and through washes and I can't see, feel, scrub, bleach or otherwise detect any difference between Kona purchased from Joanns, Fabric.com & a LQS. Plus Kauffman says they don't do 2nds...I've never found a slub or anything wrong with any Kona from Joann's so that sounds likely to me.
Although at my local stores, they recently jumped up their Kona from 7.99 a yard to 8.99 a yard, making it not such a great deal even with a 40% off coupon. And the selection is even worse than ever, I feel lucky if there are 4 or 5 Kona colors on the shelf. I wish Joann's would stop their weird "overpriced but use a coupon and it's reasonable" pricing schemes and would just price things reasonably right from the start. I would shop there more.