I recently got an Acer Iconia W500. It's similar to Asus' EEE Transformer, but a little more powerful and runs Win 7.
I was in the market to replace my old PMP. All I wanted was a usb host for hooking up a portable hard drive, enough processing power to run nice videos and not pause noticeably between songs on a playlist, and a decent screen. There was absolutely nothing out there that fit these criteria. A tablet was the closest thing.
So now I've got a device that I might browse the web on a little bit when I'm somewhere with wi-fi that isn't my desk. It does all my media easily. I'll probably do some artwork on it. It is powerful enough to run art applications, including Photoshop and possibly even ZBrush, so long as you're not pushing dozens of layers or millions of polygons at it. It's good for sketching, basically.
The only reason I didn't go for a netbook or laptop: I didn't think I could get away with having one on my desk at work, which is where I'll mostly be using it to listen to music 4-6 hours a day. I wanted something that I could easily whip out of my bag to do simple things on quickly in a large variety of situations, the most important of which is the potential to show off my art portfolio.
So it has its place... but anybody who thinks it's going to replace anything is crazy. I can see how casual users would opt to get a tablet/'netvertible' or the like instead of a pc if all they plan to do is listen to music, watch videos, and do a little browsing/word processing... which admittedly is a lot of people.