I had the same opinion for awhile, I liked the overall product and concept but didn't particularly want one. Until I got a chance to use one more extensively in the last month or so. So now I have an iPad 2.
As great as iOS is on an iPhone/iPod Touch, its even better on an iPad (with apps scaled/designed for the iPad of course.)
The form factor is really nice, much easier to carry around and use than my MPB. That's just the nature of a clamshell with thin unsupported screen, vs. a solid aluminum slab. And it's light enough to grab and take to a lot of places. Not as portable as an iPhone, but more portable than a notebook (I can't afford an MBA, and the tablet has it's own advantages/disadvantages vs. a clamshell.)
I have a large backlog of movies that I've never gotten around to, and the iPad w/ earphones is really great for watching in bed at night. Problem is I find myself continuously going past my self-imposed deadline (first half tonight, the second half tomorrow) and waking up tired.
I find typing in landscape really easy. Not quite as fast, but mainly due to being slower to make changes or correct errors. The actual typing is really fast for me.
I do agree that the utility may be limited unless there are a couple of specific uses that you really end up preferring doing on the iPad. The same would go for any product or form factor- many people have no use for an iPhone/smartphone. For me I think watching movies is that main use, and then a bunch of other secondary uses behind that.
Finally, the more iPad revisions are released, the cheaper older iPads get on the secondary market. So something that you wouldn't pay $500-$600 for might be very desirable at $250-$300.
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The IOS devices are very weak when it comes to storing and manipulating a library of files. I have files on my home computer that date back over 20 years, but on the ipad I will just expect to have a library of media files such as movies and PDF's, and maybe an album of photos. To me much of the ipad functionality is as a portable device that brings media to me. It could not begin to replace my real computers.
Apple has macbooks and now macairs if you want a very portable full power computer. They may someday bring out a tablet with the power of the macbook, but it would probably have an OS besides IOS on it, or they would have to develop some kind of "finder" functionality into IOS.
One interesting outcome of the limited internal file system is all the cloud services that are now available. Not just a Dropbox app for example, but Dropbox support by many other iPad apps.
It's not the same exact thing of course, but works really well for me (since I love Dropbox.)