I don't have the 4 yet, and not sure I really want to actually.
It does alarm me when Apple things removing something is better for the consumer, specially when the device has always had it.
If a customer has gone from an iPhone to also have an iPad, they are used to that button.
So sitting in that boardroom at Apple and someone saying "I know, let's take that button away from them, so they have to do it in the settings options" does seem rather odd to me.
My guess is that the thickness of the new one, doesn't allow to "fit" the button or the internals of it, into the new casing.
The other reason I am unsure about switching, is because it means I have to get a new case for it, and I rather like my case!
For a system that's a little bit quicker, a mm thinner, and actually a bit taller... no, I don't think it's worth it.
If you have an iPad Air, and want something smaller, then yes, I bet it would be a brilliant move. Partly coz you are already use that loss of the mute switch.