I won't go that far but i will say an iPhone serves me better than many (any?) portable device that I've used. Being always on and always in my pocket makes for great utility. Admittedly it takes awhile to adjust but if you let your iPhone be a tool it will be very beneficial to own.
People laugh when i say one of the great things about iPhone is the ability to carry documents and notes around with with you at all times. If your work involves knowledge that is a great asset to have.
I also think that this is why people recoil at the idea of a smaller 5-7 inch iPad. They just have trouble grasping how other people work. More so they can't grasp the idea that size is important especially when you are carrying a lot of other stuff around. Electronics may have gotten smaller but when you add everything up it can be a lot of mass.
The problem is that people like you also don't get what a tablet is for and relegating the device to a "leisure device" completely misses the point of the iPad entirely.
It certainly can be a leisure device but it is a sign of poor imagination if one can't see the benefit for other activity.
You completely miss ALL the jobs that an iPad will benefit greatly such as field engineers (that's what I am), doctors/nurses, warehouses, taxis, couriers, etc.
The list could go on for ages.
Well I'd say if you question the device you aren't being open minded. Without even trying i see new ways to use iPad almost every day.
As to iPhone 4 i also gaze at it with lust. Mainly because a lot of software kinda sucks on iPhone 3G already. Even at that iPhone 3G has to be more capable than half the computers I've ever owned. In many ways I'm amayzed that i can carry as much computing power as i can in my pocket.
In any event the thing with iPad is that it is effectively at the Mac Plus level of development. The potential for the device is simply huge.