Firefox is great because of all the extensions, but it can be buggy and slow at times.. For an alternative thats almost as good in most ways and better in some ways try opera.. its totally free to use, and they god rid of the banner adds. Its been around a long time and is very featureful. I use it except for when im at work becuase firefox has some handy extensions that make my job much easier, but opera is definately has firefox beat with speed and stability. Lots of really cool unique features too.
http://www.opera.com