It's really well done- the opening screen has a nice layout and makes it easy to find all of the app's functionality.
My favorite feature is the ability to "clip" coupons to your iPhone and then use them at the store- no printing required!! I did run into a small hiccup when trying to use one of my discounts at my local store (they couldn't figure out how to enter it), but seeing as they've only been open for two weeks now (and I'm so excited to have them there), I'll chalk it up to inexperience.
Other app features include finding JoAnn stores nearby (ummm, yeah, I've been known to do this on travel...a lot!!)...
...and browsing for products, including access to customer reviews.
That's quite a lot of functionality for a little app! Here's hoping that Michaels and Hobby Lobby follow suit soon.