Mining has been a pretty terrible investment, IMO, for a while now. There is pretty much no hardware released in the past year or more that is expected to ever even break even.
I've been mining for 15 months now, with a variety of equipment, currently 7 TH/s. From a fiat perspective, at today's bitcoin prices, the total return on investment (equipment + expenses) has been -50%. As in, if I'd put the fiat cash under a mattress and bought bitcoin with it today, I'd have twice as much bitcoin as I was able to mine. But hindsight is always 20:20, it could have worked out just as easily the other way around. I'm just going to hold and wait and see what happens. I have a hard time making any argument in support of purchasing mining equipment right now, but clearly with the newly skyrocketing difficulty others are drawing different conclusions.