I am using the latest OSX from Apple on my 15" powerbook and have it linked to my treo 650. The 650 is actually a unlocked cingular phone with a t-mobile unlimited internet plan sim in there. I used shadowmite's DUN patch and linked with my PB. I downloaded a generic modem script and used internet2.voicestream.com as the dial up number. It works great. I am very pleased with this. Speed is pretty good actually! I just ordered a car charger for the treo so I can have internet on the road!