I recently figured to figure out how to tether my iPhone to my Mac and I intend to use this to upload lots of photos (anything up to 1GB a month). My download limit is 500mb... But what's it like for upload?
The 500MB is your total data allowance so both upload and download. However, its a kind of soft limit where after you breach the allowance, it gets slowed down till either you pay for more or you get to your new billing period where it resets.