Yes I have this app. Yes it works with the S3 and AT&T.
HOWEVER - It works on my laptop that I already had it installed on and using with my Samsung Skyrocket. Version 3.50a if I recall of PDANet. I tried to install the computer end on a netbook that I occasionally use and I couldn't get it to successfully install. It had its problems detecting the phone. Yes I for the netbook I did install the newest drivers for the phone and I tried telling PDANet it was a Samsung and I also tried 'other'. I didn't fight with it very long to try to get it to work other than that.
Again, it does work on my laptop that already had it installed and I did NOT install new Samsung drivers on it. I use it in the Wired USB tether mode.
First time PDAnet x64 in windows would not install phone driver.
Temporary install Klink demo (another theathering prog) on windows,
and next time you run pdanet it will say that a android driver is already installed.
click no and everything should now work, it did for me.
(typing this post with pdanet3.5 app and samsung s3 at&t, phone: settings/developer options/usb debug mode)
Foxfi was removed from Gooogle Play. Here is your fix. System settings - security - allow unknown sources. Download and unzip the free attachment. FoxFi _WiFi Tether w - o Root_ v1.9.1.zip This will, allowing you to wifi tether your playbook for free.