Its an ebook reader, made to compete with the kindle and the latest Asus one (whos name i can't remember).
For that purpose it will be very good - finally one that has enough power to do things like turn pages quickly and have something crazy like a backlight (sony: take note!), and I bet the iBookstore will work really well, as iTunes does.
It will also work well for browsing the web - thats one thing I use my HP TX2 for in tablet mode as you don't need a keyboard when you have multitouch/gestures etc for browsing the net.
However that is about it really - apple have really missed a trick here i think, they are missing a key feature..a stylus! Adding stylus input would mean it could be a proper note taking device (with an apple version of Microsofts amazing OneNote) which a device like the iPad is perfectly suitable for and it could also work well for graphics design then, allowing it to double up as a graphics tablet. This *can* be done with multi touch capacitive screens - the HP TX2 or Dell XT/2 range proves this (thanks to n-trigg) and that would make the iPad so much more appealing..would have a purpose other than reading ebooks then. I predict this will happen eventually but until then...I won't be going near one. I suppose I should be grateful that Apple have messed this one up as it saves me £500!
This will sell by the bucketload for a while though as Apple will do a great job with the marketing, and heck if they really do a good job with ebooks it may well be justified for that market, but as a tablet or "Pad" computer? No its pants.
edit: oh and I forgot the last big thing they made a mistake on - it's not widescreen...and with 1024x768 resolution it's not going to be the best for video playback..they A4 cpu (which is suspiciously like the Snapdragon in specs isnt it? 1ghz arm with built in GPU...) can cope with 720p so I hear..so surely they missed a trick there too? Crazy..