I have IE7 and Firefox installed on my computer. In my opinion, Firefox works A LOT better; it's faster and more stable than IE7.
You don't have to uninstall IE7 to get Firefox. But you can definately have them both installed (and running at the same time). When I want a stable, fast connection, I always use Firefox. (Though, for some reason, it takes my computer a long time [like 30 seconds] to open Firefox... It might be a weird issue with my computer.) But for downloading, I use IE because I don't like Firefox's download manager.
In IE7's defense, it's a lot better than previous IEs. It even colors your parent-child relation tabs! IE should come already installed on your computer if you have a Windows Operating System.
Hope that helps.
P.S. Here's another suggestion: Opera.
Downside: Opera 8.0 doesn't allow you to use gmail's chat function, but Opera 9.6 is now out. Opera also is a BIG change from IE or Firefox. Look at the source below to compare the three next to each other.