I have been playing with my Eee pc, as well as a similar one I ordered for my wife a few days after mine arrived. Hers is a few months more recent, but a lower end model--no webcam, and only 4gig storage.
The included OS is fine, but upgrading to the latest versions of software is not as easy as it should be-I wanted Firefox 3 especially. It was not in the repositories for my computer, and there was not enough room on my wifes to add it after doing updates.
Rather than learn my way around the Xandros-based stock OS and figure out which repositories work for Eee, I have changed to Ubuntu-based operating systems on both of them. (Both are versions of Linux, and both based on Debian Linux) My wifes is now running Ubuntu Netbook Remix, a version of Ubuntu specifically for netbooks. Newer versions of Firefox, easier to add (and rem ove) software. Netbook remix has a slightly different interface-apps are accessed via the desktop, which has tabs along each side for categories of programs, and the selections appear in the center. This would be ideal for tiny screens, but I am not sure it is necessary for the 900 series.
I wound up using Eeebuntu, another version of Ubuntu, specifically designed for the Eee hardware. There are microphone and webcam issues with the stock kernel in the Netbook Remix, and I want to be able to use Skype on mine. Eeebuntu has a kernel designed specifically for the Eee hardware. The microphone still isn't configured quite right, but with some setting changes it works--Unfortunately I have not figured out how to keep the mic sound from routing to the speakers. (Easy-Peasy is a version that uses the same kernel as Eeebuntu, but the Netbook Remix interface--I will likely switch my wife's Eee to it soon)
Eeebuntu is closer to a standard Ubuntu interface. I am not sure I like the "task launcher" bar at the bottom--I think I would prefer the usual task bar, but set to auto hide, and I'm likely to set it to work like that. This the biggest difference in interface between eebuntu and the standard Ubuntu.
The version of Firefox that comes with Eeebuntu came with 'compact menu' and 'Smart stop/reload' add ons, that allow you to eliminate a row of toolbars without removing functionality--both add ons that I have used on full sized computers. I added a set of plugins that Lifehacker recently featured--Permatabs mod, faviconize tab, and Better Gmail. I always have Gmail and Google Reader open in the first and second tabs. With this combination, these tabs are reduced to the size of an icon and permanent, and the Gmail icon has the number of unread messages in the icon.
I also set up the touchpad so that it does not click while typing--with the tiny keyboard on the Eee, I was constantly finding that I had moved my cursor to the middle of a different paragraph in mid-word.
I am getting used to the keyboard, but I still have some problems finding the right shift key, and hitting enter instead of the quote or apostrophe key--as a result I am avoiding contractions... I have typed on worse full sized keyboards, and it gets easier the more I use it.
With Eeebuntu, I am very impressed with this little computer--It does just about everything I need in a computer, while remaining compact and very portable. I wold almost call it the J-frame of computers...With the added feature that if you can wait for these to show up on Woot.com, you can pick one up for under $200 including shipping.
I do not know how necessary changing operating systems is--people with less Linux experience may be completely happy with the stock setup.
If you are not going to give up your full-sized computer, you might also be interested in Synergy--This is a cross-platform app that lets you control one computer using the keyboard and mouse of another, just by scrolling off the screen, even if the computers are completely different operating systems.