that's really a stretch right there. in order to look at the phone to browse and whatnot, i have to take it away from my ear, meaning unless i put it on speakerphone or bluetooth, i cant hear anything.
if i'm connected via bluetooth, that means the phone is in my holster or i'm driving. i have no need or desire to browse the web. so basically the only time this becomes a factor is when i've got someone on speakerphone.
i'll still take my ability to multitask over this very situational dilemma. Never once in my life have I ever been on a call with someone and said "damn, I wish I could use my data without having to hang up." it's more like "i'll look up the directions and send them to you." chances of any iphone user actually using this feature is slim, and when it does happen it'll be just because they can, not because they need to.