Golly, I must have the best Joann's ever, based on all the negative comments here. I did not realize that Joann's takes competitor's coupons and have never tried to use them there. But I've got a Michael's withing walking distance of work, a Hancock Fabrics about a 5 minute drive from work, and both Joann's and Hobby Lobby on my 15 - 20 minute drive home from work, so if I need something, I just use the appropriate coupon at that store (except for Michael's, since I know they do take competitor's coupons).
I get Joann's coupons in the mail and online, so I always have plenty for when I go. All of Joann's personalized coupons have personalized codes, so they can only be used once. I've been told that trying to use the email coupons more than once alerts the system to watch out for you and if you abuse the email coupons too much, they will kick you off the list. Since I don't do this, I don't know if it's true or not.
I've never had a problem using my coupons. But I always read the fine print. When they have their coupon commotion and specify the type of item on the coupon, I always pay close attention and make sure I don't use the wrong one. As long as the coupon code is different, they will allow you to use multiple Joann's coupons.
I also have the 10% off AQS (?) discount. I use it on anything that I did not use the coupon on (except, of course, for the items Joann's generally excludes from coupons).
My advice: fully read the coupon before trying to use it.