Why would I want to install Ubuntu -- or any form of Linux?
Linux is free -- in many senses of the word. It costs nothing, and it's also free of corporate control and restrictions on how you can use your media. That recently prompted digital-rights advocate Cory Doctorow to switch from Apple Computer software to Ubuntu. He was concerned, for example, about Apple's proprietary software locking up his personal data. "Every day, I add thousands of e-mails to my e-mail repository," he said. "And for so long as Mail.app is using proprietary stores, that's an ever-growing liability."
Compared to Windows, Linux is also relatively free of malware attacks. For example, security company Panda Software records about 300 pieces of malware targeting Linux systems, versus more than 100,000 for Windows machines.
This is a very important question, because it answers, "Why bother", and this answer is fairly accurate and I would probably say something like this. However, something to add is that it gives you total control of your own computer, and by using it, you'll learn a huge amount about how your computer works. If you look, linux reveals the intricacies of how your computer works, and by the nature of open source, you see how many other things work. In proprietary software, you have no idea how it was built. All you have is an instruction manual which tells you how to use it. However, the instruction manual may be sufficient for basic usage, but in order to tinker and improve, you need to be able to get INSIDE. That is my $.02.