I would actually recommend buying SP hardware if it was sold from stock and for a reasonable price.
I wonder sometimes why european/US manufacturers seem to unable to fully grasp the idea of selling from the stock or a short (2-3wk) preorder.
What exactly is the difference? Is it small manufacturing facilities, risk aversion, upfront funds?
European/US asic makers also do not care about market share and in one case (KnC) are unable to adjust the price to market conditions.
I am still at a loss as to why KnC did not continue to sell Jupiter into jan-Feb or why spond did not continue to sell Sp-10 as long as it was selling with a profit (maybe it wasn't, I don't know). This seems to completely contradict almost any other business that I know of. Typically, you continue to sell an older model if you are still making money with it until there is a new model. I don't see anything unique to bitcoin that negates this possibility.
You stop selling an older model if the cost to produce that model is weighted against the amount of profit you would get by maintaining it. So if they were going to need to make another chip run and spend $100,000 but only sell $50,000 in SP10's, that'd be a stupid business decision. I'm sure the old models of some cars sell great, but automakers replace them anyway. Now sure, in the beginning had ST had a crystal ball to see the future, they'd of known to produce more chips and then would be better prepared to have just the perfect amount before the SP30 started selling. However, crystal balls are rare and not nearly as effective as we'd like them to be, so they had to go with a business plan they felt made the most sense. They didn't account for such high demand. Oh well...
As for why do folks preorder. It's an interest free loan and locks the customer down so you can fine-tune your manufacturing plans. It's unfair to the buyers, but so long as people preorder, the manufacturers will keep doing it.
That said, the only way to make really great money is to be able to buy the cheapest miner with the most hash at the earliest possible instant. So that you get the most hash for your dollar. So many people who preorder understand they are taking a risk to be first in line. Though, it's only really worked for those guys who got the first round Avalons. I suppose in the early days of BFL if you got in right at the start for the Asics that ran at 1.5th, you'd of made serious money since their prices were about half what they were later when Bitcoin prices went up. Otherwise, most everyone else is buying on hopes that BTC will rise, or working off very thin margins now.
I think most mining is a money loser. Primarily because most of the hardware manufacturers have been terrible at delivering their products on time. Almost every single one of them has been a failure.