I had no problems with C Bar whatsoever. On certain nights they had all-you-can-drink alcohol for $20 a person from 6pm-10pm. Granted, there was a list of pre-determined drinks that you could choose from but we tried everything on the list and were pleased.
C Bar is located on the ground floor of the main building of the Stratosphere. It's next to the casino and just behind the main entrance to the hotel.
We tipped the bartender very well right after we paid....rather than waiting until we left and had awesome service the entire time. The two bartenders were tag teaming and we NEVER ran out of drinks and they were made perfectly every time. We had such great service we tipped again before leaving.