julie, I'm not Dave but as far as I know the auto-resize still kicks in at 1000 pixels wide. Personally I resize mine to 800x600 and I find that the lower resolution of .jpg over .gif is - in most cases - a fair tradeoff for faster uploading speed. (I'm on ISDN but that's not the fastest connection in the world.)
Terry, thanks very much for the info. I usually work with the .jpg format for the web. And as for uploading speed...well I'm on satellite, it works really well for downloads but the upload times are more like dial-up. :-)
Seems GIF's are better for images which have more solid areas (like print screens or web graphics), but JPG's do well when images have a lot of color variation and textures. I size mine at 640x480 unless something closeup where I want more detail to show, and I save at about 70%.