How many Microsoft developers use the MSDN Library? Probably not many because I've just read a blog post where someone recommended not even installing it. I have to admit that I never even opened the Microsoft Document Explorer until I learned how to add my own notes as a custom help collection. Now I use the Microsoft Document Explorer every day. I'm a bit concerned that I am duplicating content that is already baked in so I've spent some time browsing the MSDN Library. You can save interesting help topics as favorites and here are a few of my favorites:
Colors by Lightness - ms-help://MS.VSCC.v80/MS.MSDN.v80/MS.WEBDEV.v10.en/css/workshop/author/dhtml/reference/colors/colors_light.htm
I have some color charts in my notes but these light colors are better for web design.
CSS Enhancements in Internet Explorer 6 - ms-help://MS.VSCC.v80/MS.MSDN.v80/MS.WEBDEV.v10.en/dhtmltechcol/dndhtml/cssenhancements.htm
This includes a diagram of the CSS box model.
C# Programming Guide - ms-help://MS.VSCC.v80/MS.MSDN.v80/MS.VisualStudio.v80.en/dv_csref/html/ac0f23a2-6bf3-4077-be99-538ae5fd3bc5.htm
Lots of information about some of the more advanced features of C# like Generics and Delegates.
Visual Studio 2005 IDE Tips and Tricks - http://msdn2.microsoft.com/en-us/library/bb245788(VS.80).aspx
Plenty of screen shots here. This is actually a live link because you can save any web address as a favorite in the Microsoft Document Explorer.
So why don't developers use the MSDN Library? There are several improvements that could be made to encourage you to use it. First and most importantly it needs to be customizable so you can take ownership of the information. You ought to be able to annotate the MSDN Library with comments and sticky notes like so many other applications allow. Unfortunately, you cannot even highlight text and retain it. It is possible to add your own help collection as I have done but this requires a lot of effort.
Second the search needs to be improved. I am unable to search my custom help collection and it does not even appear in the index. It would require a massive effort for me to create an index even though all of my help topics have keywords in their original web page format. I also never get anything in Local Help when I conduct a search no matter how I fiddle with the options to get it to search local help.
So what about the Community Content in the Online Help? Anyone can comment or add to the online content. Unfortunately, not many developers are bothering to do so except when the existing content has some really inaccurate information. This makes the Online Help's Community Content look like some sort of pathetic wiki that nobody bothers to contribute to.