I have an broadband line on my account, and can answer any questions about the broadband account anyone might have.
For starters, there is *nothing* different about the settings on an aircard compared to a phone. I'm using a kpc650 with prl 1050 right now. The username/password is still 10digit#@mycricket.com, password: cricket.
It is the broadband phone# that is special, and it works without a proxy, regardless of if I use it on my kpc650, or the usb aircard, or on a phone. WifiRouter works great on a mogul (or ppc6700) and no proxy is needed on the computers connecting to it. We've even tested it to work in a different market, even though that market doesn't have broadband yet (but does have evdo).
If I do configure my laptop to use a proxy while connected using my broadband card, I get the error message: "You do not have access to this site", same msg I'd get on a normal line that didn't have unlimited wap.