All you people who have just 'benefited' from the latest price drop and upgrades need to know what to expect because I know you are all, like vaisajne, feeling like you just got a great bargain.  I felt the same way two months ago when I bought my first GM contract and had it almost immediately upgraded from 4 to 9 MH/s - just like what happened last week.  That inspired me to buy another larger contract a week after the first one - I now have 59MH/s.  It felt great to have all this money coming in day after day.  I always understood that the rate of returns would drop off, but what I was not prepared for was the RATE at which they would drop off.  To put it simply the payout in BTC is roughly halving every month.  After two months I am getting less than a quarter the payout I was getting when I started.  GM announced last week that they will be bringing online a new datacenter and new ASICs.  Undoubtedly there will be much competition in the space for the foreseeable future.  I believe we can expect the monthly halving of returns to continue for some time.  I am not even going to come close to breaking even.  If I get back more than 50% of the BTC I invested  I will consider myself lucky.  

Here is another chart.  It shows my accumulated GM payouts in pink.  The black line is an exponential which shows the break-even level.  If the pink line is above the black line I will make a profit at the end of the contract.