I happened to be in the US on the launch date and ended up with the 64G WiFi model. Have been using it everyday for the last two weeks, as have the whole family.
There most definitely is a place for a tablet device and Apple's execution is for sure the most elegant I've seen so far. While it will not replace a Netbook or Notebook for many people, I see it slot in between a smart-phone and a netbook. The much larger screen clearly trumps a smart-phone while the much slimmer body makes it more portable than a netbook.
Over the last two weeks, I've watched not just myself, but my family to see how we use the device. (BTW, it's only been on the charger 3 times in the last 2 weeks. Battery life is very good.)
From a business perspective, I've stopped carrying my laptop in the car, on flights and around the house. The iPAD is more than adequate for e-mail and browsing stints of a few hours at a time. The main apps (mail, browsing, etc.) have been re-written to make use of the larger screen, so really works well. I've got a number of newspapers and books on the device and these update automatically, so if you have a gap you've got the latest news with you. My last local flight was the first time I did not buy any mags or newspapers but read a number of newspapers on the iPAD.
The on-screen keyboard is more than adequate to type longish e-mails and, just like the touch-screen phones, takes a bit of getting used to, but thereafter you're quite fast and accurate on the keyboard.
Two things are missing right now to make it a complete business tool, MS Office and 3G. As rpm said, you need 3G for full mobility and, let's face it, the business sector is stuck in Office. While 3G is on its way, no news yet for Office support (you can read Office docs, but can't create) although Apple's own productivity suite is available. Still need to load it though.
But I believe the biggest use (and impact) of the iPAD, and other tablets, will be in home use. It's probably the first device that will become a universal information and control tool for the whole family.
Again, watching the family (from 6 to 76) using the device over the last few weeks showed it's more deemed just a tool (much like a remote) than some fancy computing device. It mostly lies on the coffee table and everyone uses it, from going through holiday snaps to playing games to browsing the web (including checking TV schedules) and reading the occasional book. Home control (including DSTV) is already available.
Up to now there's been a number of drawbacks in the devices available for daily home usage. Battery life, clumsy user interfaces, lack of apps and cost being the biggest drawbacks. The iPAD managed to address most of these quite well.
The biggest drawback for home usage is the fact that you still need to plug it in to recharge. While it sounds trivial, it's actually quite a big problem with most of these devices in the home. No-one bothers to plug them in to recharge. I would like to see an inductive charger for these tablets so you can just leave them on the coffee table to charge.
I bought my first tablet device in the 90's and have used nearly every iteration since then in the search for this "converged device" that will replace many of the day-to-day gadgets we use in the home. But cost, screen issues (size, resolution and brightness), poor battery life, limited applications and crappy GUI's meant that most of these had limited or no success, especially as a whole-family device.
But I'm quite comfortable to say that the iPAD is the first iteration that ticks most of the boxes.