I usually work in Photoshop first, and then jump into ImageReady when I'm ready to create rollovers/animated gifs...
But, everyone has their own way of working with regard to Photoshop/ImageReady. I've met people who do things SO backwards that it makes me want to pull out my hair. However, at the end of it all, what we've created looks identical - just that mine took 10 minutes, and theirs took 1 hour.
(BTW, I'm sure they look at my workflow and go, "Dear GOD! What are you doing!!!!
)