This can sometimes be painful when the PERFECT sentence must be changed to avoid a nasty orphan. But it is also another chance to change anything that you thought was perfect at the time, but months later, sounds sort of lame. So this is a good thing. I'm loving this whole process.
Except when you suddenly notice that all the spelling is Canadian, and the publisher wants it American. Panic sets in when you realize that you don't really know all the words that are different and you google it and see that there are A LOT of words that we spell differently! I may have to send the senior editor some chocolates.