If the current upward trend in difficulty continues without a massive increase in price, ASIC miners based on the 28nm process due to ship in December are not likely to make ROI.
Here's the data giving you an example as to why(scroll down for the actual example):
https://docs.google.com/spreadsheet/ccc?key=0AkguHfgeV7J1dFpDSm84NzZSZ28zQnBWamtkOTduaEE#gid=0This is based off of Bitmine.CH's Coincraft Desk, however it applies to pretty much every ASIC.
If you still want to make such a purchase, please keep these values in mind
229.6MH/$ mininum needed at 869.3MH/W in order to make ROI at a Bitcoin price of $170 USD
If the difficulty continues to rise as it has(if it stalls before/on december for a few months they will make ROI), and the price does not rise to/past $170 by december, it is unlikely you will ever make your money back.
Just some friendly advice,
If you happen to find an ASIC that meets these two requirements:
229.6MH/$ minimum <-- more important
and
869.3MH/W
be sure to link me.
Thanks and God Bless.
