Internet Explorer 6 vs 7

Hey all…

I have been assigned a new project testing an application that we use internally on IE 6 to see how it performs on IE7.

Not being a big fan of IE in any version, I have opted for one of its competitors.

My question for those who use either on a regular basis… where do you see advantages/disadvantages and what features or functionality have you experienced having conflict with existing web applications and/or websites?

All insights are very much appreciated!

Thanks!
Cupcake

[Edited for clarity]