A great example would be one of my Canon scanners. In Windows XP/Vista, you will need to go through and install the drivers for it from the manufacturers website. The same can be said about three out of the four wireless dongles I own as well. In most Linux distros, they work with zero configuration, while in Windows Im left searching for drivers...which is tricky to do without Internet access.
The downside to all of this out-of-the-box compatibility is that some rare devices will not work at all, regardless of what you do.
Despite this becoming less of an occurrence, it is frustrating nonetheless. In the past, we have been asked to utilized our Linux distribution's hardware compatibility lists (HCLs). The idea behind these lists is that users can report back on what is working and what it required to get the hardware operating with the desired results.
My experience has been that these lists are nearly useless on every level. Often dated, they are too limited in scope and in general, lacking other needed information that the user might need to be aware of before purchasing the device. So even with all of the effort that goes into creating these lists, were still left playing very much into fate's hands.
The solution? Common sense.
First of all, buy your computers pre-installed when considering a notebook or netbook. Unless you are looking to "tweak' things to meet your needs, you will find life is going to be simpler if you take this approach.
Second, stick to "brand names" when building your own desktops PCs. Brands such as Intel, NVIDIA, ATI are brand names to make yourself familiar with when looking to build from scratch. The above mentioned video card brands will allow you to experience the wonder of the 3D desktop, while also ensuring that you will not have "mysterious" video card headaches as you go through the Linux installation process.
Other hardware such as motherboards and other related components are generally nothing to be concerned over. I have used countless old and new configurations, and at no time have I ever run into a problem with regard to a motherboard issue. Im sure that rare instances exist, but they are hardly anything to be concerned about.
Existing PC builds
Most of the problems people run into when trying to install Linux with existing PC builds comes from a lack of understanding of the dynamics of what they are trying to do. In short, the individual is often trying to install Linux onto hardware initially built for a Windows install. Remember this as we continue.
The easiest way to find out if your existing setup is going to work well with your selected distribution is to grab a LiveCD and boot from it. This way no changes are made from your existing Windows installation, while still allowing you to give the PC the compatibility test. In most cases, you will find that everything works just fine.
Connection to the Internet, check. Sound played through your speakers, again check. Yet for some reason, your monitor's resolution looks a little out of place? Perhaps you are having the ever-annoying 800x600 resolution by default?
Assuming youre using something like Ubuntu, chances are solid that you will able to correct the resolution issues after installing the proprietary video drivers for the video card post-operating system installation. While the open source drivers that come for both cards are fine, sometimes you will find that you can get a better monitor resolution with the proprietary drivers than the default open source driver.
Great external hardware support
One of the things I like about bleeding edge distributions like Ubuntu is the fact that I can connect nearly everything I own and know that it is going to work well out of the box, speaking of external USB devices of course.