Personally, I love them. I read them, I write them. Standalones really do have their place, but I've yet to write a book where I didn't want to know more about secondary characters and story lines. Series can accommodate that perfectly. In fact, originally, Midnight's Ghost was supposed to be one book. The ending happened and that was all she wrote - literally. But when I let the story sit for a little (as I do with all my stories) I realized there was more to the story there. Questions I hadn't answered that I wanted to know - not just as a writer, but as a reader to. Just what did happen to Taran's father? And how the heck did Wallace break out of Widow's Bay? Those were questions I hadn't answered at the end of the book and ones I needed the answers to. And the next book in there series was born. Interestingly enough, the premise of the next book already lent itself to another book and viola - a three book story arc.
There's a recent book I wrote where I kept telling myself that I was going to write a standalone title. No series, no connections, nothing. Didn't quite work out that way. LOL
So, how do you feel about series?