SSH through tethered AT&T iPhone 4
I'm thinking about signing up for tethering through AT&T, but I'm wondering about something. I currently have HandyLight and use it (rarely) to tether my MacBook Air to my iPhone. This works perfectly for web browsing but I'm unable to connect via SSH to my web hosting server (DreamHost, FWIW). Getting my email via IMAP through Mail.app also fails. I've noticed this same problem on certain free WiFi hotspots, especially those that make you "log in" through a webpage redirect upon first loading the page.
My question is, can any one confirm that SSH through official tethering (whether via WiFi Hotspot, Bluetooth or USB) works or does not work?
If I sign up, I'd be giving up my unlimited data plan on both my iPhone and iPad, so I don't want to do it if I'm going to end up with something that doesn't really work for what I want to use it for.