To begin with the rez is small. The smaller the rez the more your pH will swing and the quicker your temps will as well possible causing all kinds of problems. You'll have to add water back a lot more than you would with larger systems. My friend bought one and he told me the pump is also very weak, a bit underpowered. Since it's the winter I doubt you'll have to worry much about heat but warm water means a greater chance of root rot.
If you're only looking to grow an oz or 2 per cycle it might meet your needs.
Here is the most impressive grow pic I could find in one
Take a look at his temps and how many lights he's got going, not to mention co2. Most of the pics of plants in this system that I could find are plants in veg, which makes me think that most people fail somewhere during the grow and stop taking pics. Even this guy would probably have a better yield if he took them out of there and made a hempy bucket (a few bucks) or a dwc (40 bucks).