I just bought one here in Houston -- it's in a 3 gallon bucket. Nice colors on it (definitely blue, and some with a bit of lavender as well). It doesn't like too much sun (as with most macs), but the leaves and blooms are just lovely. Looks to be somewhat compact (compared to the 3 gallon ES in the bucket next to it).

This is a grower selection - Greenleaf Nursery, of Oklahoma - of the old standby, Nikko Blue. Supposed to be a better performer. In your zone, should perform very well for you. In my zone, sometimes there will be flowers, some years just nice green leaves...

Sounds like it was developed by Frank Dutra's Nantucket Hydrangea & Botanical in Nantucket, MA but, like Brian says, it was developed by another grower based just north of me. Go here for just a tidbit more info...

http://greenleafnursery.com/index.cfm/fuseaction/plants.plantDetail/plant_id/2794/genus/Hydrangea/index.htm

and here....
http://www.tulsaworld.com/scene/article.aspx?subjectid=41&articleid=20090607_41_D4_Nantuc329406

It is for sale all over here with NB side by side. Surprisingly, and I go off topic for a second, I also found a couple of nurseries with Invicibelle Spirit a-n-d Bella Anna both on sale on the same nursery. Barely starting to bloom. If you are looking for these Annabelle Clones, this type of set up would help you view and compare them side-by-side. Some people have not liked the color of IS.
Luis

Here is a link that might be useful: Nantucket Blue

Thanks all-wonder if it really is remonant--its in we will see.......

Well after this winter it came back from the ground and has 5 or 6 large blooms-well pleased as it joins rebloomers-either from the crown or truly remonant I do not know.