With the coming dump of massive ASIC hashing power in the next 3-4 months (Cointerra Terraminers, Kncminer Neptunes, etc.), it is going to be very difficult to ROI in a decent timeframe. Cointerra is starting to ship their 1.66Th/s machines and have beaten Kncminer to the punch. Probably won't see any Kncminer Neptunes until end of April or early May. If you have sufficient capital, would probably be wise to spend half just investing in bitcoins (which will probably double in value by year's end) as a hedge against the further increases in mining difficulty.
Anything under 1 TH is going to be effectively useless. I managed to dump my operation before it got any worse. At this point, I'd say mining really isn't profitable any more unless you've got a huge farm running or planned. Although if you have that kind of money, you're probably not worried about much. I would definitely move to investments. It's much safer that way.