I don't mind open endings, I know a lot of people with very strong opinions on open endings but I quite like them in certain books. I don't mind a stand alone having an open ending, when you aren't completely attached to the characters. It's interesting to conduct your own theories about what happens and to hear the theories of others. It's just a bit different and can be really cool when done well.
Although, that being said, for a series I would prefer a closed ending. When you finish a series of books and you've become really emotionally invested and really attached to the characters, you want to know what exactly happens to them. I'm not reading up to six or seven books to not find out exactly what happens to the characters that I now love like my own family. That's just bordering on cruel.
But, if I were writing which I tend to like to do, I have a couple of preferences. If I were writing a short story, especially on a time limit, for example, at school then I tend to use an open ending a lot. Though, if I were going to write a bit of a longer story then I would like to give my characters a full ending.
I also think it has a lot to do with genre, a dark, mystery book would be a great one for an open ending. Although, if you were writing something like a romance then I, as a reader, would probably want to know what happens. Romance probably isn't a great example because I can think of quite a few ways it could go where an open ending would probably work well. My point is, it depends on what the book is about to as whether I would prefer an open ending.
The main thing is, I don't mind a nice open ending. When they're done well they can be great. They can provoke some interesting conversation topics and make for awesome blog posts to be honest. I like them as long as it's not at the end of a series, I'm absolutely fine with them.
What are your feelings on open endings? Which do you prefer?