I've been using this for a couple years now and it's been fantastic. Just the Compose Key support alone is a godsend. The swiping takes some getting used to, but with practice it now feels second-nature.
I don't feel like I make more mistakes than I typically do with any other smartphone keyboard. One particularly annoying mistake I make all the time is hitting backspace when I meant to hit a character near it, but that was always a problem with other keyboards and my fat thumbs, too.