What are the major differences between IE7 and IE8 that a web developer should know

internet-explorer-8

I've just downloaded IE8, which replaced my IE7, but that's okay because IE8 has a 'compatibility view' which is meant to render pages like IE7 (not sure about the JavaScript).

I was wondering if there is a listing on the internet of all major differences a developer should know between the versions. I've searched Google a bit but haven't found a satisfactory listing.

So, what should I (or any other web developer) know about getting my site working optimally on IE8, and what are the major differences between the two?