actually, you havemoreproblems than you realise, esp if it's an early version (like 6) since IE has some funny quirks when rendering a lot of css. most developers will make sure a site degrades to these browsers gracefully, so the site still renders looking asnice and as close as possible to the intended design as possible.
in real terms, it just means the web is a more beautiful place with a modern standards compliant browser. such as firefox, or safari.
so to sum up, if you switch, pages will load faster, they will look nicer, you'll get rid of most of the bugs you experience throughout most websites, and if choosing something like firefox, you open up a world of brilliant plug-ins to add extra functionality in, just browsing the extensions section on the mozilla site may change your mind...
Changed from internet explorer to google chrome now. it's alot faster, but will take a while to get used to it.
I'm an oldie so don't follow tech stuff to well.