"No great shakes"

• "I've been better"
• "It's not great, but not terrible either"
• "I'm lukewarm"
• "I'm not really excited"
• "It didn't thrill me"
• "It's nothing special"
• "I can't get excited by it"
• "It was fine, I guess"
• "Who cares"

Wiktionary Word definitions in Wiktionary
a. 1 mediocre; lackluster; unexceptional; uninspiring. 2 apathetic; unenthusiastic. interj. (context slang English) (non-gloss definition: Expressing indifference or lack of enthusiasm.)