It's a tricky one. I suspect that even with ebooks, the hassle involved with going in and correcting the finalised files is probably not worth it (especially given that you often sell about half the copies in the first week, before you'd even get any corrections) -- but that if you are preparing new files for a different edition, e.g. a new electronic file format or releasing a print edition, then it is worth it.

autopope routinely asks for errata reports when one of his dead tree books is about to get a new edition (hardback to paperback, first edition in a new country etc), and I've seen some of my other friends doing the same thing from time to time.