Hello Scott
Due to IE being constantly targeted by hackers and virus writers, security updates are added to IE, and they can slow the browser down, however with the next security update that comes along it normally goes back to full speed.
If you have Java running then this can also slow the browser down.
IE is integral to Windows but if you are using XP then you can go to the Set Program Access and Defaults on the Start Menu, or System tools and set Firefox as Default.
IE is a fully featured browser and so comes with everything as standard, (Including the Kitchen Sink) were as Firefox is a basic browser to which you add only the items you require, and so it is much faster, unfortunately due to its popularity it has now become the target for hackers and virus writers, (Used to be only IE that was targeted) so make sure you keep it and your security updated.
Consider also the Opera Browser http://www.opera.com/, which I find superior to Firefox, and would be the browser I would use if IE did not exist.
Food for thought.

Bill