I haven't been tempted, but there have been other ladies that I've seen that I've wondered what it would be like to sleep with them.
My girlfriend and I have both felt this way before during our relationship and we have agreed that as long as we don't act upon it, it's okay. It's actually a pretty nice understanding. She has told me it is okay for me to flirt with other girls as long as I don't kiss, touch, and I am with her at the end of the day. I feel the same way about her. We're both natural flirts, anyway, so it's hard to keep that corked :p