Weather Display, WeatherCat, WeatherSnoop, and wview all support Davis serial, USB, and IP loggers.
I've been using the WeatherLink USB for Mac logger since installing my system September 2011, and have had no problems. I only tried WeatherSnoop and Weather Display for a short time, but WeatherCat (and its predecessor LWC) has been running 24/7 just fine.
I don't know if there is a physical difference between the Mac and Windows USB logger. I've read where you can convert one to the other, but I've also read you don't have to. I do know that two people on the old LWC forum tried DIY loggers and had intermittent and mixed success, and I think both ended up getting Davis loggers.
Steve