LPT: If you feel you had great service by a waiter, tell them! I'm sure it'll brighten their day for the rest of their shift.

I know from my job as a server, whenever someone compliments my service or tells me that it was "fantastic" or anything, it really makes the rest of my shift wonderful. If i'm having a bad day and someone tells me that, it immediately makes it better, or at least in my case it does.

So if you feel that they did give you great service, tell them, because i'm sure they'll appreciate it.

Edit: In addition to your well rounded comment, give a nice tip that reflects how you feel.