The $10.00 Add-On according to Sprint is not for 4G service, its to ensure that there will be the bandwith available for this data hog of a device. It gives you unlimited data whether you use 3G or 4G.
I don't think I said it was $10 for 4G. It's not. It's $10 extra for all Evo users, 4G or not. Other users, like HTC Hero owners, get unlimited data without the $10. Sure, Sprint does have great plans, even with the $10 addition. But they set a high bar for themselves, so if they're charging Evo users an extra $10 for the privilege, I certainly have the right to evaluate that addition.