I, of course, didn't pay for my iPad. Which kinda blows the cost-effectiveness argument out the window for me. And along these lines, if iPads were to grow on trees, I'd pick at least a half dozen of them to be distributed through my living space. Because that's how cool they are.
Once you own an iPad, it's a total Steve-Jobs-Love-experience.
The web browser, for a non-desktop device is great. It's almost, but not quite, identical to using a desktop web browser. The big problem is flash and certain AJAX features. Standard HTML, from 90s-grade HTML 2.0 to modern HTML5 written in a generic fashion all work just fine. Flash doesn't work, and I can't say that this is entirely a bad thing. Some AJAX features assume the user is going to have a mouse so some sites are a little flakey. Some features of Flickr work, some don't.
I came into the iPad already impressed about how upgrading from Mobile IE on a 240x320 display sucked compared to a WebKit-based browser on an 854x480 display. The iPad browser on a lower-pixel-density 1024x786 display is even better.
Furthermore, some of the apps released for the iPad are similarly awesome. The Netflix app is great, for example.
The big thing that I didn't quite get until I started using it is just how inconvenient a keyboarded device is. Any laptop-form-factor device, from a small Netbook to a giant 17" laptop, is never going to feel right if you use it standing up. It just begs to be put down on a table and used. But in a slate form factor, you can hold it much like a clipboard. Or cradled in your lap. It doesn't have the natural on-the-table sort of form factor.
The battery life is great. Much is made about how a Kindle has several days of battery life, but I think this matters less than you'd think. The real barrier is a rational day of usage and the iPad will work quite well doing that.
I think the biggest software deficiency is largely that, even if I could pick a half-dozen from an iPad tree in my backyard, it still begs for multi-user use. See, a smartphone or MP3 player is usually a personal device. "My" phone is a Motorola Droid. "My wife's phone" is an Apple iPhone. But the iPad is a coffee-table device, something that any member of the household might use. My wife and I have it configured with dual accounts in some things like Tweetdeck and Mail, but it's totally clunky.
The biggest hardware deficiency is that the wifi is really short-range. I suspect this contributes to the long battery life... although I'm sure being able to only radiate signal through the display and being otherwise an Aluminum farraday cage probably doesn't help. Really, it begs for 3G data, although I suspect that I'm not willing to pay for the 3G service for a second device...
The iPad does not have an integrated protective shell to protect the screen from scratches. My usual preference for carting computing devices around is neoprene sleeves, so I got a Belkin-made sleeve. The Apple-branded sleeve has an impressive built-in stand, but it otherwise didn't feel right. I did find that, even in the Apple store, some of the sleeves were just Netbook sleeves branded for iPad use, whereas the Belkin one looks like they built it around the shape and size of the iPad.
I'd rate the keyboard speed as being below what can be achieved with a real keyboard. As such, I've got the idea in my head that I'd like an external keyboard of some sort for it.
I also think that there are times where it's unacceptable to use the device as a slate. My wife was trying to prop the iPad up on the airliner table so she could watch movies on it and that just didn't work out.
The iPad dock in general is somewhat limiting. It's intended to be stationary and used as a picture-frame, I think. It's mostly using weight to counterbalance the device, which means that it's really not going to feel nice in your handbag.
Looking at the iPad Keyboard Dock, it's really clunky. It's like they glued a keyboard to the standard dock. If it folded up and was light, you could pack it as an optional accessory. But it's pretty much designed to be used from a single location.
Apparently, the Apple Bluetooth keyboard or other Bluetooth keyboards will also work with it. Most Bluetooth keyboards are either too large, too expensive, or both. Looking at some of the high-end devices out there, the Apple one is positively economical in comparison.
I think I'll mostly wait this one out. I suspect that either Apple will work on more Apple-branded accessories or one of the other manufacturers will come up with something. The Neoprene sleeve makes it transportable, so when somebody has a good solution for keyboard on the iPad, I'll get it. Or we'll collectively realize that the iPad just doesn't need a keyboard and that any solution that tries to add one is just a bag on the side.
Right now, I don't think there's nothing preventing somebody from making a similarly great Android-based device to counter the iPad. At least for the features I use. As time goes on, opportunities for Apple lock-in will increase.