If there's one thing I wish I did more, and more consistently, it's playing to clicks in more situations.
Moon is absolutely right, it's a tool, not a crutch; however, it's a tool you shouldn't be afraid to use, and to use ruthlessly if the band sitch requires some tempo policing. However, it's not an overnight acquired skill, it requires some hours put in to learn how to bury the click, to shift back and forth around the beat, and how to drive the band with it. I also agree that a click works even better if the band can hear it too ... but that also means that *they* need experience in playing to clicks, and that's something that not all musicians seem to believe in doing. "Hey man, you're the drummer, tempo is your job." No, it's everyone's job, IMO.