Making the leap - MX2004 to CS4?

Hi,

I’ve been using MX 2004 pro for a few years now at a fairly superficial level just for website updates/enhancements, little educational things, and little personal animated birthday cards, etc. I have just recently started learning action script, which I’m getting, slowly but surely.

Anyway, my question is: how much different is CS4 from MX 2004? i.e., am I looking at a huge learning curve? I don’t mind huge learning curves when I have lots of time on my hands, but I don’t. But I would like to keep my software up-to-date, since I just got a new computer with Windows 7 on it.

Thanks,

Sarah