Tim,
Providing the number of units that will be available is not that big of a deal. Even a range like 20-50 units would help. I understand if you put a low number on it, you think it may hurt sales in the beginning, but I think being forth coming and honest about your ability to deliver the product will ultimately drive up sales in the end. If you leave this vague, and a bunch of people pay their money up front just to wait months to get their product you will loose customers.
If you allow people to pre-order and pay when the product ships, then there is no reason for people to ask the questions you do not want to answer. When tunzes came out with their latest 60xx series they revield how many units they expected on what date and it did not hurt the sales of those units. I would even suggest that the limited quantities they posted drove up sales.
Here we are 12 business days from the announced shipping date of the product and all we have is the word of a company with a poor history of delivering on that word and a "rendering" of the product and not even a photo of the actual product. I hope you can understand my skepticism and questions. Bit me once, shame on you. Bite me twice, shame on me.
Two questions you still have not addressed are..
1. If I wait till your production catches up with back orders, so that I can order when they are in stock, will I still get the upgrade deal?
2. Are you still giving the one year warranty extension as promised?