3.5 stars.
There's not much to say about this place except that everything here was M&M branded. You name it - mugs, shirts, toys, kitchen stuff - all have the words "M&M" on it. Honestly, I wouldn't buy anything here because I don't need or want any of the stuff. Sure M&Ms taste good but do you really need a M&M-branded shirt or cup? lol It was just fun to look around at all the floors (3 I think) and see nothing but M&Ms.
If you are a hardcore M&M fan, then this place is a must see; other than that, there's nothing much to see.