One thing I have had the fantastic experience (NOT) of with a recent couple of App updates is that the App I'd bought months ago was now becoming a "rental" and I would be charged 3, 6, 12 monthly periods at an $x.xx rate. This was explained, almost hidden away really, down the LHS in the fine print below the UPDATE box.
Another App that had been free, a magazine for Newsstand, was now becoming a $99 sub and this would be charged automatically to my Apple Acct. It even stated it could not be cancelled! I only found these facts buried in the second level(!) MORE INFO. For someone like me who up till now just made an assumption an Update was always free and a good idea it really is important read and look through just what is going on, especially the MORE INFO.
Now the only problem is dealing with having the red bubble on my AppStore icon permanently with a number in it depicting the number of updates I don't want. I for now have gotten rid of it in the end by ceasing to use the App and fully erasing it.... I wish there was a way to not accept an App update and not have the messed up App Store Icon which looks like it's going to come, based on the number of paid for Apps I use on my iPad 2.