A "good" dealer in blackjack is professional, knowledgeable, and efficient, handling the game smoothly while engaging with players in a friendly, respectful manner. They follow the rules consistently, keep the game moving at a fair pace, and are quick to answer questions or resolve issues. On the other hand, a "bad" dealer may lack focus, make frequent mistakes, and cause delays, leading to a frustrating experience for players. They might be unprofessional, show signs of cheating, or fail to maintain a positive atmosphere at the table. Ultimately, a good dealer enhances the gaming experience, while a bad dealer detracts from it.