Joel Spolsky is the world's most readable teaching geek. He is a fantastic manager of programmers, and was a programmer from Microsoft in a previous life, and even the lead on some of the early versions of Excel. If he says it, I pretty much believe it.
In this long article, he teaches why Internet Explorer is so unbelievably complex to build. And along the way he addresses the reasons Vista is so unpopular, and why it really should be unpopular. The article is as simple as it can be made, but it still gets pretty complex. If you can hang through some of the tougher parts, you'll be way ahead of the class when browser discussions get started.