I've had half a dozen of their turbines and currently still have an i500, i2000, and a Heli 2.0 up in the air. I had an i1500 for a couple years, only pulled it down to replace it with the 48v i2000. I believe the i1500 and i2000 are easily the most watt/dollar you can in a consumer turbine and the only DIY turbines with similar output I've seen that cost less to build were Hugh Piggot style axial turbines. I'm not quite so impressed with their smaller body turbines like the i500, they work but they need a lot of very steady wind to really build up any power. I've had the Heli 2.0 up for a year and a half or so and it's been a monster. I think the i2000 is a slightly better watt/dollar ratio but the Heli makes about twice the power in the same wind.
My i1500 I spent the first year being very mean to. There was one storm that the wind spooled it up to over 3000w, blew up one of my batteries, then free-wheeled the rest of the night. After getting the battery bank set back up it spent the rest of its time with me running just as nice as ever.
We don't get as cold here and, honestly, seldom gets below zero, and usually if it's that cold it means there's no wind...I can't really say how well they perform in the extreme cold but I can't see any reason they'd have problems. I've had them running in freezing weather, though, with rain and snow and hail, as well as all summer in 105+ heat and sticks and dirt flying, and the only failures I've had are these silly connectors they like to use to connect the stators to the slip rings.
I will say my goal has been to see when and how they break, I always recommend that if you see a heavy storm coming that you shut them down rather than risk the blades or stators. I f someone is looking to buy a turbine, though, I always recommend the i1500 or i2000.