The $10 per month sucks but it's well worth it to dump that moment I bet. My wife had the moment and she couldn't wait to upgrade. She hated that phone with a passion.
As far as the $10 per month being a "4G Charge," a lot of people erroneously call it a 4G charge. It began life as a 4G charge, but even 3G smartphones use mass amounts of data over feature phones. That is why Sprint decided to change the name of the $10 surcharge to a "Smartphone premium data charge." Customers have been flaming Sprint over that charge everywhere, but it really isn't that bad when you figure you have a smartphone with unlimited data.
I agree that when you come from a smartphone that was grandfathered in without the charge, it stinks. I had the Hero, the wife had the Moment and my sister had the Hero also. All grandfathered in without the charge. Add $30 on monthly, when we upgraded and it was a tough pill to swallow, but well worth it to have a phone that wasn't buggy and running an OLD version of android.
I heard of people who would bring their Hero/Moment/Optimus S in for service and replace it with a different phone (go from Hero to Optimus for example) because there were none of the same phone available and they had the $10 charge slapped on. That sucks, at least they could upgrade to a newer phone that isn't crippled...