You don't need to spend extra on the fan to get accurate readings. If the fan were the only way to get accurate readings, they would be standard on every station probably. I love Davis. Just got my VP2 back in February. She's awesome. Although I am one of the few that's actually had good luck with Oregon Scientific as well, My WMR100A, nearly 4 years old, survived being dropped 14 Ft top side down (battery changing accident. Still works today. still accurate. I got my Vantage Pro2 because after 4 years with my WMR100, I'm not predicting it will last much longer. Of course I hope my predictions are wrong because the OS is a good station. But not as good as Davis. Lacrosse would be a great candidate for worst stations. But if you ask me, Davis is your best bet.
Also; Sunfish is right. In arid conditions where standing air heats up quickly, the fan helps move that air around. In areas where the 100 Ft of pavement rule is imposable, it helps. My station faces this but the temperature is accurate. However one thing about the Davis VP2, unless you want to separate the thermo/hygro (NWS specs 5 Ft off ground) from the rain gauge (NWS specs 2 Ft off the ground) you have to compromise. I have mine mounted 10 Ft off the ground, about 18 inches off the fence. Mine uses the standard radiation shield. There might be some slight heat issues. But the ISS gets some good wind where it is that makes up for it not having the fan. However can't it helps the rain gauge very much.
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