Certainly, some get Priority. Why does this suprise you? If you are a customer spending a million a year with a supplier, he is going to take care of you.
When you pre-order, you will never get to see who else pre-ordered, or even know how many. The number of sales a dealer has is a very closely held figure.
Deal with a local dealer if you can, and get to know him. Generally, small dealers will keep you informed because small dealers need the business very badly.
That said, I've ordered from Adorama many times over the years, and corresponded by e-mail with my rep. He is always plesant and doesn't make promises he can't keep. I tried a couple of orders with Amazon and gave up. Now, I just buy locally unless its something only available at one of the big stores.
If you are having a problem with B&H, e-mail Henry Posner and he will try to help. http://boss.blogs.nytimes.com/2010/10/19/seven-steps-to-managing-your-online-reputation/
For Adorama, try Helen Oster, she is very helpful. e-mail helen[at]adorama.com
But, do not expect them to tell you that you are number 124 of 8756 orders, or give you a delivery date when they do not know exactly when or how many cameras they will get.
There is no excuse however, for some of the rude responses, even though they are really tired of people asking for information they cannot supply. Henry or Helen will be happy to remind those responsible of the need to be polite.