I have been using Onenote since it came out, and that means for several years. I find it indispensable. The handiest feature is the quick-launched "Side Note" feature, that sits in the tray at the bottom right of your screen. I can launch this little window with a click and type a thought immediately, or drag something (text and picture) off of the web. Anything you type or drag and drop is saved pretty-much immediately and automatically.
If you have Outlook 2003 or later, you can coordinate this program with Outlook.
If you are into learning or gathering information from all over and like to keep it and file it, this program is for you. You can collect and organize all sorts of information and later, if you wish, clipboard it into Word or Excel or other program.
The search function is handy too. You can search a notebook, a section of a notebook, or all your notebooks (you can create a notebook for each major subject area, like personal, work, art, music, vacation trips, etc.)
Very nifty program, well-thought-out and constructed, smooth-working.