I didn't like any of the BETA Firefox releases, but I must admit Firefox 1.0 is a big improvement. It loads webpages much faster than IE. For example, my online hosting account control panel, takes 2 mins to load in IE, and freezes up while doing so. Firefox loaded it within 30secs.
Firefox takes a bit of getting used to, but after a while it starts to grow on you.
On the downside, there are some extended features from IE, that do not work, such as the coloured scrollbars. Also, some JS that aren't Netscape enabled will probably fail to work correctly.