So what makes Mozilla so much better than Explorer? (technically and opinion-wise)

It comes with an pretty good basic HTML editor (Composor).

It's open source, so if you are capable and want to change something you can.

Add-ons that let you tweak performance to just the way you like it.

I like the spell check. Also the pop ups almost know when to open in a new tab or the same one.. like magic! Plus the add ins for FF are awesome.

The main problem with Explorer is that it was written in great haste when, about a decade ago, Microsoft realized that the Internet was important and they needed a browser FAST. It was thrown together very quickly, and consequently badly. And it is very difficult to recover from bad foundations. This has been aggravated by Microsoft several times trying to force standards on the Web, then having to back off and implement the Web standard.

Mozilla, by contrast, is a second generation browser implemented relatively at leisure. It therefore has much better foundations for development.

Firefox 3.5 is faster and also has tabbed and private browsing features. The fact that you can personalize it is what makes it such a cool browser. Plus you get lots of themes and extensions with Firefox. Some of my favorite Firefox extensions are Screengrab, Billeo and Read it Later.

If Mozilla were really so much better, more people would use it.
So probably it is better for some people. It is not better for the many.