The "interface" (how you interact with it)--it has a touch sensitive
screen and understands "gestures". It's closer to being an appliance,
and is lighter, portable, and you can upgrade it by replacing it every
year or two. My wife has one. IIRC, It doesn't even have a USB port.

Exactly. I will replace mine every 2-3 years depending on iOS version.
Unless there is something I cannot do with my current iPad, I see no
reason to upgrade. However, upgrading every two years does give you
the opportunity to get at least 50% back on your original cost which
makes upgrading more frequently more attractive.

The portability and long battery life seem like they might be attractive to
a degree. For me - I've never really felt that my laptop encumbered me
enough to look for a different technology. I certainly do not understand
why the absence of a USB port would be considered attractive. As for the
interface - my Galaxy S-3 has one of the best touch screen interfaces out
there (currently...), and it is interesting, it is sometimes very
convenient, and it is sometimes just technology. In otherwords, I like a
lot of the aspects of it, but a lot of touchscreen is just whizbang.

Laptops are large and heavy, especially if you want a decent screen
size and/or it serves as your main computer. I have a 17" HP laptop
that weighs about 21lbs. No way am I carrying that around.

With the advent of cloud connectivity and storage, there really isn't
the same need for a USB port. As long as I can stream my videos, etc,
then why bother with more acessories?

I have a friend who uses his iPad while on vacation to view, sort and
upload his photos to his home machine. He also loves the GPS ability.

A friend has a Samsung and only uses it to read. She hates that she
cannot delete apps or even re-arrange them to suit her needs. Now she
has an iPad for everything else.

So far, I would not want to be without the familiar things like a mouse,
etc. But... I've never used any of the pad devices, so who's to say?

It's hard for many people to adjust to new ways of doing things.
Except for kids. I will say I found somethings a challenge, but I like
a good challenge. I still have a desktop and will for some time due to
the work I do, but I will certainly make use of any new and better
tools if they make my job and life easier.