I've had my TEMPEST system for about six months now.
As far as wind goes, it does seem to do OK. Precip/mist doesn't seem to affect readings as much as some other units.
However there will be some weird out of the blue gust peaks for no reason. It only happens during the day (this may have happened a total of 5 or 6 times in the past 180 days) and I suspect it may be insects flying near or through the gap.
I will say this though, last December we had a major snow to zr event back to snow that stopped all cup anemometers that weren't heated, also prevented an unheated professional ultrasonic from working correctly and the TEMPEST was still working. There was .5 in of ice accretion on the unit with lots of icicles in front of the gap. I was surprised it was still working!
Ultrasonic has its merits for sure but one must realize its not without drawbacks either. This is why if you value your data you're going to have multiple instruments of different types whether its cups, aerovane, pitot, et al. Of course you could spend tens of thousands of dollars on instruments only to be wasted on poor location!
For home/personal weather stations, I would recommend a traditional three cup anemometer. It's a proven design, with good bearings it will last long and only fail in extreme conditions (debris strike or severe ice storms/rhime conditions).