Yes, some do come supplied with GNU/Linux.
Here are some quick facts:
- There are different versions of GNU/Linux (or just Linux usually). Some are better than others. For some reason, most of the netbook manufacturers including Linux supply poor quality versions. Others, like Ubuntu and Fedora, are better.
- It is difficult to learn, depending on what you want to do. This is simply because most people are used to Windows; Linux is different, and so in that sense is 'hard'.
- It has a 'man in his shed' ethos about it, meaning that sometimes you have to get your hands dirty and think about the nitty gritty stuff (i.e., it's not always Windows point-and-click, but usually is).
- Most versions supplied with Netbooks are deliberately scaled down, with simple large icons for your web browser, word processor, spreadsheet application, etc. This makes it easy to just use, even for a regular Windows user.
- Again, it's best to try it out in a shop and see if you think you can live with the size of the keyboard and screen, and the system itself.