Beverley, just a clarification - I'm not talking about poor grammar in dialogue where an author is trying to convey a regional accent or the authentic dialogue of a poor, uneducated homeless kid. I mean books where the author and/or her editor clearly knows nothing about punctuation, tenses and so on.
As for telling a story which grabs the reader's attention, I couldn't agree more - and I have my doubts as to whether editors always know best there. Having said that, as with reading fanfic, poor grammar is one of the things which will always jerk me out of a story - and when it's a book I've paid good money for, then I'm not going to give that author another chance in a hurry! :p
Wendy