It's terrific.I only like the Kira spelling. Keira looks to me like surname Keir + a, and Kiera looks either wrong, or like it is pronounced to rhyme Sierra.
Simple, common but not too boring, pretty but not too frilly, with a little strength/spunk. Preferred spelling is Keira, then Kira, and Kiera last. Kiera makes me want to pronounce it Ky-ra (to rhyme with eye), instead of keer-a. I also like Kiara.