It's recommended, but not strictly necessary. If you do
install, don't worry about your profile data (bookmarks,
addresseses, etc); those are not removed.
Happily, it also imports all your Netscape bookmarks if you
decide to switch over.
Interestingly, it also resets the default "edit this page"
in IE to Mozilla's composer (heh, turn about is fair play).
That also is an easy fix, but it caught me off guard. I
rarely use IE, but when I do it's either to browse a
microsoft web site or edit a web page using Word and I'm
just as impatient as everyone else here.
