Full disclosure: I work for a commercial printer, so the opinions are based on our (Prinergy) workflow.

In a perfect bound book, we do not shingle the pages. If it's saddle stitched, then creep is automatically applied based on a formula we use that takes the stock and number of pages into account.

As far as spreads go, in a perfect bound book, it typically does not lay flat so you don't really notice the missing image, that's not to say there will not be any image missing. We do have a couple of customers who take it upon themselves to adjust the images when a spread crosses the gutter, but we don't ask for images in the PDF to be adjusted.