You have to understand their views on your investment.  It's not currently possible, but let's say you spend the $274 to buy that miner today and can get it today.  To the majority that post in here this means you just invested ~2.3 BTC in a product that will never earn ~2.3 BTC over it's lifetime.  By this definition their suggestion is to simply buy BTC and not mess around with miners as you will have more money in the end whenever you sell that ~2.3BTC.  If you insist on getting a miner though, be prepared to wait.  While BFL has plans to complete all pre-orders by the end of September, it's not looking likely, then they have all of the orders placed since April 5th to go through.  I doubt you would see an order placed today before Dec 1, but I could be wrong.

If, like most people, would are interested in how much money it can possibly generate, that is a complete unknown, as it is dependant on your share of the total netowrk, the ever-changing value of BTC and how badly you want to get the money from what you mined.  If you can view this as a long term investment, then you can earn more than you spent in USD.  You would be better off though buying BTC and holding it, if you have the patience.