I'm in the exactly same boat as you are.
I live in Toronto, I own an iPhone 3G on FW 3.0, jailbroken.
I used that website trick, and selected Rogers.
I also have the 500mb/month data plan only, as I didn't use 3G much.
I only got the data plan in the first place because I was being charged for
using cellular data when I didn't even use any.
The phone was constantly downloading/uploading some data without
my acknowledgements or intentions.
So anyways, the tethering works great on 500mb/month data plan.
My only concern is, whether we would be causing problems with Rogers.
Do you think that they could find out that we're doing this on their end and
try to charge fees or in worse case, take this problem to the law?
Thanks.