Hi, I just seen this thread.
I had built my 3 decks deck using the dek bloks and have had no problems at all I live in NE michigan by Lake Huron and we get a butload of snow and freezing temps for most of the winter, and I couldnt be happier with them.
I built my pool deck so it is under the rail and it didnt heave one bit maybe 1/4" if that even but I left about 1 1/2" for the heave. My other two decks the same for the front and back deck. My back deck is 14x24, it is attached to the pool deck and not the house it is a true floating deck and is only a foot or so off the ground. The pool deck is about 48-50inches high and is about 10x20 , I have a 52" side wall pool. The front porch of my house is also with dek blok and it is 8x16 and about 30" off the ground. I have never had any trouble with the decks heaving at all and just made adjustments so that if it did it wouldnt hurt anything at all. Give it 1 1/2-'2" clearance and you should be fine. If you make the deck higher than 30inches just put in bracing and its no problem at all. The thing is strong as a deck dug in and doesnt move and inch when walked on. I did use double beams on it too and did lag bolt them to the posts too to make it extra strong. My pool deck I built last year, the back deck has been up for about 5-6 years with no movement or problems at all too. Front deck up 2 years.
I swear by the dek blocks if you dont want to do the extra work to dig holes. Also you dont need to have a ton of deck bloks either as they tend to over do the deck block thing in their plans. But if you know basic deck building the dek bloks can be used almost like post holes filled with cement. I think my plans called for about 18 dek blocks to be used and I only had to use 12 or so for mine. But too, the plans I had were based on a rectangular deck and mine has the rounded area that took away from some of the rectangular decks plans for the dek bloks. Just do your reasearch online and you should be fine if you have basic deck building knowledge. Some for instances on my plan they called for an 8 ft section to have 3 posts and dek bloks on it, it only needed two for that span with a double beam to support the joists. Its little things like that where you can skip the dek blok in the middle of an 8 ft span, that isnt needed.
If anyone has any specific questions let me know I probably had dealt with it using deck blocks. Also going to HD is good to have them draw up plans , but I find that going to mom and pop lumber yards that have deck building software works a little better as they seem to be able to modify plans better than the HD software and they tend to know more about structural integrity of decks and the such and they can tell you where you can skimp and where you shouldnt.
Hope this helps
BRIAN