Hopefully, someone can comment on the Acu-Rite or a comparable station. I guess I can live with longer update intervals to stay on my budget.
Acu-rite sends updates every 18 seconds from the outdoor unit(s). As someone else said, Davis updates much quicker. There was a comparison table somewhere (Weather Underground?) that listed the update frequencies by manufacturer/model, and if I recall correctly most of the others were longer than 18 seconds. This is a general limitation of wireless sensors that run on batteries. If you can still find a wired unit, it should be the fastest updating option.
I recall reading somewhere that the Acu-rite anemometer has a pretty good low speed mechanism, and can detect down to 2 mph. You might want to dig around to find the details if this is important to you. They also have a 3-in-1 sensor that does wind speed but not direction which is cheaper, and it was on the shelf at Lowes last time that I looked. Haven't read much about it though, but suspect that it doesn't come with a PC interface option in the box if that was a requirement for your application.....