I've been using SwiftKey for a while now. It does some things that drive me crazy from time to time, like sometimes the swyping predictions are pretty terrible. But for the most part it works well for me. I also like how I can minimize to one side of the phone or the other for better one handed use. I think the stock keyboard can do that too though. Probably the biggest thing I like about it is how easily it learns words and then it stores them and can sync them across devices. Plus I'm so used to holding down the delete key to delete a word at time that it drives me crazy when I use other keyboards.