They are not so different to the casual eye.
You have to be careful when buying a netbook though! Why? Because some vendors make their own version of Linux that is rubbish. It's a stupid thing to do because they can take almost any version of Linux and use it so long as they call it something different. Legally!
Lots of people who buy a netbook change the operating system before they even use it.
The main Linux distros (distributions) supply a specially-for-netbooks version of their own Laptop Linux. This is to make sure all the buttons and the wifi, SSD etc etc work without doing anything. Sometimes you do have to fiddle around a little but not often and its easy because so many have already done it. There are tutorials.
There are even better choices to be made depending on which netbook you buy. In stores in the UK, right now, is an edition on Linux Format (or one of those Linux magazines) that recommends which netbook goes best with which Linux. Ubuntu for one and Mandriva for another etc etc. They have also reviewed each netbook for its battery power, weight, size, processor power and all the rest.
What you need to ask the vendor is "does this machine allow me to install new software AND does it allow me to access the command line" The answers to both questions must be "yes". Unless of course you would prefer that your netbook be more like a phone with certain apps available and that's all.
I highly recommend Linux but you need to be careful. You should email me with any questions and maybe tell me what you want the machine to do like: "can I use my ipod on it?"
You can even try the linux apps on your windows machine before getting the Linux laptop. iTunes is available, I'm sure, via WINE but there are better alternatives. I would list them but I'm not sure that you have an ipod.
Some of our best tools are:
miro (media player, torrents, you have to see this to get it!)
songbird (media player with internet browser! ipods)
boxee (lots streaming TV and media player)
scribus (dtp)
abiword (word processor)
open office (data base, word processor, spreadsheet, powerpoint-like-and compatible presentation app, draw)
inkscape (vector graphics - http://screencasters.heathenx.org/ http://www.inkscape.org/)
GIMP (photoshop-for-free with similar tutorials and books as Inkscape which makes them both very exciting for if yoiu ever need them!)
gnumeric (spreadsheet to go with scribus, abiword and inkscape if you don't want the heavier open office - all 4 are very quick but brilliant)
gnome-do (exceptional way of controlling everything from one place - its like predictive text - guessing what you will type eg you hit tab and whatever I type open you tube with that search title but it works on locating files, emails, writing emails EVERY app on your PC. You tube it (search for gnome-do and while you are there search for ubuntu))
Here are some more apps:
http://thedailyubuntu.blogspot.com/
Now look at this but look at Categories on the top left hand side too
http://www.getdeb.net/
And:
http://www.gnomefiles.org/
That's enough to keep you going, I think.
Please don't hesitate to get in touch