They tell you it is unlimited but it is 5GBs. On the other hand that was for broadband access connect (mobile broadband connect) so since all data usage (tethered to pc or from your phone) is added up as phone data usage it should be unlimited. Its very tricky, that's how they get you stuck with big bills. And I worked there for four years and I am still confused!
Nevertheless, I too am using EasyTether and I have yet to see crazy data charges on my bill.