Problem is, when you get in on the first month or 2 they have a much higher price. Most seem to leverage the price just to keep you on the verge of thinking you'll make more than your investment back. The only value I can see with buying early is the resale value of your miner can still fetch you a decent return because people are still buying them. The price of Bitcoin factors in a great deal as well. But then, it might be just cheaper to buy coin than to mine it.
The pre-orders scare the crap out of me. I hate paying for something with no guarantee that it will be sent, and there are soooo many scams out there.
Higher price you are correct... Also probably correct in getting good at ebay to sell off your hardware.
As for pre-orders yeah don't think I will ever go down that road. I have seen a pre-order for the Prospero X-3, 2TH/s for 6k, expected in may. In may if difficulty is at 75% per month (last 30 days ~73%), you will still be in the hole unless difficulty levels off or price goes up (Even more then today).