I would not use the call button for a drink or other service element. It is rude because it signals to the FAs that I need something urgently, and it interrupts whatever duties they might be carrying out at the time. Instead, I would just stand up (if the seat belt sign and conditions permit) and walk up to the galley to make my request politely.

I would never use the call button except in an urgent/emergency situation. For example: I once used it when a kid sitting next to me vomited explosively and we needed a bunch of paper towels to clean up. I was not able to stand up to get the towels myself because we were on final approach. The FA was happy to help.

My $0.02.