I honestly kind of like it. There are names much worse than
Kayley out there. It sounds bright and happy and I like
Kay as a nickname.
However, I would never use it. It was too trendy and already seems dated. And all those spelling variants are confusing.
I also like
Hayley and I like
Eilidh, which sounds like AY-lee.
Kayley looks fine to me (better than many popular spellings of it) but I would choose
Kayleigh. It just seems more substantial and grounded because of the song. So it has at least a bit of history.
Kaylee,
Kayley,
Kayleigh,
Kaley, Caley - all look okay to me. So does Ceilidh. I don't really like
Kailey and
Kaylie but they are acceptable, of course. Strongly dislike Kayli, Kaeli,
Kayly etc.