I have CS3 and I use the Image Preview feature. Every time I go to export an image that way, I am presented with the settings I used the last time.
When you say it was the last settings you used, is that on the same image, or a brand new image?
That's for a brand new image.
I often make screen captures and save them as PNG24, and that's what's waiting for me whenever I make a new image. It's also the image format I get when I make a slice, simply because it's the last format I exported to.
I agree with you, though. I wish there were a way to set/override a default, rather than depend on "what you did last," because that just isn't very reliable.
To be honest I never use the image preview, but if its the way to have my last selection remembered then I will start using it.
I think I will make a wish, see if the Export option can actually have the optimise settings available, so if you haven't changed it to the correct one, you don't have to cancel out of export, then change it, and then back to export. I will also wish for a default optimise setting, so you can create your own, and have that as the default. If enough people wish for the same, or similar, then it might just happen.