Great thread, I just signed up having got a WS90/GW2001 (reports as GW2000, advertised as 'upgraded' version on Amazon UK).
Just thought I'd pop in as I have a small airport/airfield close to me, approx 1 mile away as the crow flies, and have friends in the area with weather stations (which prompted me to get one!).
I've mounted mine 1M above the apex on the gable end of the house, it's as tall as I dare for now. I live in a flat area and have good open space infront of the house, quite open space behind and am the tallest house on the street, so hoping to not have to much turbulence.
I wasn't sure the best place to mount it, but the concensus of those with weather stations near me as the higher the better..
Comparing to the local airport:
Barometric pressure - out the box, only 1hPa out, but was 3-4hpa over night when it was cooler.
Wind speed/direction - It's only been 1 day, but checking frequently between the Airports METAR and my station is quitr close, direction is very stable and tracks nicely, windspeed I'll need more time, The weather is atrocious at the moment, but people in work have been checking my station and theirs/METAR this morning and all commented they wish theirs correlated that closely.. I have had some gusts up to 74kph with the METAR showing gusts up to 37knots (68kph) and compared to some stations around me which are reacting badly to high wind speeds, mines very stable.
Precipitation - Too hard to say, it's picked up rain very reliably, but nothing to compare, I've within 10% of surrounding stations, no one is standing out as more or less accurate, it certainly picks up drizzle early and it would wrong to say it's wildly inaccurate, although time will tell, I have 7 stations within 5 miles, so plenty to compare to.
Temp/Humidity - within 0.1C and 1.5% respetively to the METAR data.
Niggles - I wired up a 12v (2A) supply to the unit, hoping it is true that should avoid having to change batteries, I popped in Energizer Lithium anyway, although the 'feature' of the hardware reading weird battery voltages with an external supply connected seems true and how I found this forum!

I could get a WH40 or similar and mount lower down, I have plenty of nice easy to access places I can pop that.. I certainly would not want that so high up, I'm OK to a point with heights, but nearly 9M up was a bit unnerving even with a very sturdy set of ladders tied to the house!