I've been signed up for Buzz for a few weeks, and so far, all I've gotten are offers good in store. Nothing so far for e-books or that I can use without going in. I think it's an attempt to drive traffic to their B&M stores, and not to compete with KSO.
So far, if memory serves, I've had offers for things like a cup of coffee free while I'm in the store, and 20% off of a single in-store purchase. There weren't a lot of details in the text message, so I don't know if that could have been used on Nook or Nook accessories, and since I don't need any, I didn't go try it out.
I did get one right around the holidays that was 30% off a single item, and I used it on a CD box set I was getting for a (late
) gift. That worked out to a pretty hefty discount, and I also got my BN credit card discount on the balance. At that time, the store staff had no clue what to do with the offer on my phone - I must have been their first one - but they figured it out pretty fast.
If you get charged for text messages, and only buy e-books and Nook stuff, it might not be worth your while. I'll come back and update if I ever get one that says it is good for digital content or on Nook/Nook accessories.
One thing I do have to say, though, is that that they promised not to send too many messages, and it's been maybe 1-2 a week, which I consider not too many...YMMV.