My thoughts...first I'll be buying one. A 64 gig Wifi model as soon as I can in March.
I think people need to stop saying "it's not a computer." Yes, it is. So are the iPhone and iPod touch. People need to let go of the traditional desktop computer/file system approach. It's needed and appropriate for a desktop computer / laptop. Not for a device in this class.
As to what I'll use it for:
1) I currently carry a notepad (~9"-12") in a leather binder to all of my meetings. I can now replace that with this which will allow me to handwrite or type notes, and my data can be searchable.
2) I work in IT. VNC and RDP clients on this will be much more useful than they are on my iPhone screen.
3) I rip my DVDs to H.264 with handbrake for AppleTV and can now transfer them via iTunes to this device for viewing without iTunes having to convert the video first and creating another file.
4) The screen and battery life makes watching this content that much better on the go or wherever I may be.
5) Perfect Vacation computer, I don't have to take my Macbook Pro with me to Disney World in June. I can offload my digital photos to it, have access to wifi, email, web browsing, upload to my mobile Me gallery, everything I'll need, sans iChat video conferencing.
6) Mobile iWork with video out @ 1024 x 768.
7) Perfect portable sketch pad, paired with a Pogo Stylus. Said Pogo Stylus will also be doing the handwritten notes if I chose to go that route. I won't have crazy Wacom 1024 levels of sensitivity or tilt but, that's fine for me.
8) I wanted a kindle for eBooks. Don't need one now.
9) I wanted a digital photo frame for my desk at work. Don't need one now.
10) Gaming. No more expensive $40.00 DS and PSP titles for me.
I would have liked a webcam. Maybe bluetooth or via the dock we'll see one, or version 2 of the iPad. I think we'll see Multitasking in iPhone OS 4. I can see how people are upset with lack of multitasking on the thing at the moment, but for me it's not a deal breaker.
Flash and some kind of Netflix streaming would be awesome, but that's all software and can change at any time.
The App store way of installing and managing software is really fantastic and makes it a lot more simple than downloading and mounting .dmg files for mom and pop. Yes, it's a downer that Apple has to approve apps, but it is a bit of quality control and there is truly an "App for that". I'm excited to see the new round of Apps that developers will amaze us with and what OS 4.0 will bring.
At the price for the device, it's a no brainer.
And yes, I have a Netbook. An MSI wind. I tried "hackintosh". The screen sucks, the webcam is laggy (under OS X), no multitouch....it has Windows 7 on it now which is....meh. I tried using it for meetings and such, I hated it.