I do not recommend buying the only reason but a powerful one, is that it is a pre order purchase.
In the bitcoin economy it is hard to predict the future, and that is exactly what you have to do with a pre-order, 90% of the time the miners get burned only on very rare occasions they win.
I recommend waiting until it sells from stock if it ever does, and then run a calculator such as
http://www.vnbitcoin.org/bitcoincalculator.phpor
https://bitcoinwisdom.com/bitcoin/calculatorand calculate if you ROI in 45 days, if you want to take some risk then 60 days, over 60 days the risk is very big and you could not ROI or only break even after several months/years of mining.
As of now none ROI below 60 days, and that includes the antminer S3, if in doubt use the calculator, the calculator will be your best friend.
Either of the above calculators should work and the results will be near identical.
As for mining pool use p2pool best payout, however it takes longer for the payout and must leave your miners running 24/7, if lots of people use it the part where it takes longer for the payout may change.
Using a calculator on a pre order does not work well since you have to speculate on the difficulty increase and that is where most fail, also in the past BFL has been over a year late on deliveries, cointerra, knc and most of the other ones have been late with no compensations, some like avalon have failed all together, so any pre order is high risk.
Even on spondoolies it is high risk if you read the forum the SP30 was expected initially to be lower consumption and have a higher hash rate, it is my understanding that there was a compensation for the lower hash rate but not for the higher energy consumption, and of course refunds were out of the question.
