Ok, to end all this discussion:
What browser:
- Still installs on Windows 98/ME? --> Opera is the only one. Firefox 2 is sloowww!
- Is the fastest? Tossup. Each week, it seems IE, Opera, Chrome, Safari, The World, Firefox release a "newer, faster, more secure, better" browser.
- Is the easiest to use? IE9 seems most basic, so IE9 is easiest.
- Is the most secure? IE -> Active-X exploits / Chrome -> Doesn't fully block ads / Safari -> Still trying / Opera -> Seems buggy / Firefox -> Best so far.
- Is the most stable? IE -> Crashes on multiple tabs / Chrome -> Getting better, not quite there / Opera -> Buggy, diminishing tabs / Firefox -> Best so far.
- Works the best? IE -> Problems rendering certain sites / Opera -> Same as IE / Safari -> Decent / Chrome -> Good / Firefox -> Good
What browser should you use?
- Older OS -> Opera
- Slower system -> Chrome
- Fast system, updated windows -> Firefox
In conclusion:
If you have a fairly fast machine with a fairly up-to-date OS, Firefox seems to have the best overall package as far as stability/layout for usability/most powerful ad blocking plugins/best user experience overall.
Firefox runs well if you have the CPU/Ram/OS to support it.
The above is from my personal tests.
P.S. IE is awful at acid tests,
.