I'm a regular user of Firefox. But while I was helping someone with their computer, I stumbled upon the new Internet Explorer 8 Beta. So I tried it in my computer.
And so far, I like it!
New features I have taken notice include the InPrivate browsing. I used Google Chrome for a short while but I dropped it due to instability. However I miss the Incognito feature of Chrome which allowed me to browse websites without leaving a trace. IE8's InPrivate is the answer. It also lets you browse privately by not leaving traces of your browsing on your computer. Close the InPrivate window and IE8 forgets everything in that window.
Another simply blew my mind as it was the last thing I expected IE to have: A find toolbar! IE had always been stuck with the infamous Find dialog which just sticks like a sore thumb out when I press Ctrl-F. I hated this, and I always loved how neatly Firefox shows a find toolbar at the bottom of the page.
IE8 surprises you with something very similar to Firefox, but at the top, just below the tab bar. But oh man, did I just notice that? I was so used to Firefox's find toolbar that when IE8 tried to surprise me with its own version, it took me a while before I realised it!
Then there is the brand new feature called Tab Groups. If you open a link from a page in a new tab, both the new tab and the original tab are assigned a randomly chosen colour. Thereafter any new tab created by a link in any tab of this colour will have the same colour. It's a bit hard to explain but once you try it, you'll understand. I found a Firefox add-on that can do the same and more: Tab Kit
There are many more new features. Check out the website.