I work intensive on websites and other digital media (such as apps) and use slices and "save for web" all the time.
When I have a big file with many slices on it and only want to save one or two, photoshop creates a preview of the whole file. This takes a some time. I often don ́t need this optimization feature, because every slice has set the correct file preset already.
For example I see that a color or gradient has to be changed on the page. I make some slightly color change at one slice (on a big image file with many slices) and start "save for web". It makes a big preview and I have to wait before I can save. One "trick" I use is to crop my image to a small size with the needed slices, save for web and the undo. But when I forget to undo and save.....its big sh** 😉
● So I only want, that there is in the save for web & devices dialog a checkbox "create preview".
● Also it would be a solution to simply save the last state of the tabs in the preview area. So when I switch to "Original" it remembers next time and only start to create a preview when I change to "Preview" or "2-Up" etc.
● A smarter additional feature would be (for me and the growing mass of people working only digital) to have a faster method to save only one slice without start a (oldschool) dialog for that. For example a small save-icon (a disk!?) in the corner of every slice. Like now with the number. The type of image preset could be adjusted in the slices options panel.