I have one and use it a lot for reading emails, document review. The typing on the keyboard can be a little clumsy. There are other netbooks out there same kind of spec but with a larger keyboard..... overall though am very happy with my mini.
Ordered one last year from Dell but fortunately as they were taking an age to manufacture and ship the netbook I cancelled it.
I say fotunately, as I then bought a Samsung NC10. Far superior machine: 10" screen, 160GB hard drive, full size keyboard, Windows XP, 6-hour battery life all for the around the same price as the Dell Mini9...
I got my mini 9 from Dell when they first came out. I love it!
My only gripe would be battery life - newer models should have the all day battery.
I have a 17" laptop but its not something that you would chuck in your bag and take with you. The mini 9 is.
I ordered mine with Ubuntu which comes bundled with open source office applications, camparable to word, excel, powerpoint etc. So there was no extra cost.
Also, it has some really cool educational games that my nephew likes.
Best discovery though is an application called stellarium - a star map that can be configured for your location so you can identify the stars, constellations etc. I even brought it to the Phoenix Park during Earth hour when Astronomy Ireland had an open sky watch event.