I bought the Eee as a second computer, since my regular laptop is just too heavy to be portable. In contrast, the Eee fits in a large handbag and weighs less than a kilo.
Having configured an advanced desktop as opposed to the more personal-organiser-style interface that is the default, I find that the battery life isn't particularly great - but it's pretty rare to be far from a power source for very long, and the Eee has so many features that make up for this.
The screen seems very small at first if you're used to a normal laptop/desktop, but once you're used to it it's perfectly fine even for web browsing and so on. Equally, you may make more typos than usual for a little while as you get used to the keyboard - but it's a million times easier than texting on a phone, and we're all used to that by now!
The preloaded Linux (Xandros) operating system is very easy to use and configure, even for a lifelong Windows user. In fact, it convinced me to make the switch to Linux on my main computer too. The tools available, such as the OpenOffice suite, are comparable to their mainstream counterparts, and can save into standard file formats such as .doc and .xls. Added to this, the machine has the advantage of far more powerful tools for configuration and programming than is available to the average Windows user, and a little research can help you get more out of your computer than you might ever have imagined. There's a ton of free online documentation for both Linux and the Eee specifically, so you're never alone if anything goes wrong. (Which it hasn't for me so far.)
You'll need some extra storage for your files. The SD card slot in the machine means that you can add a few GB of memory which just sits in the machine, and you can add USB devices if you need to.
This is a fantastic machine, and I have been thankful on so many occasions that I bought it.