He laughs. The small, harmless trick is a nice surprise for a shinobi, trained in jutsu for the purpose of combat. He's sure Aang has more destructive abilities, and just as sure that Aang doesn't enjoy using them for that purpose. This fits his personality better.

"Very nice," he praises Aang sincerely, an amused smile still on his face. "Let me change and we can do some more!"