I must say

Pro Tip 1/3

Subtle Agreement

Use when you agree but want to acknowledge others might not feel the same way.

I must say, your idea does have some merit.

Pro Tip 2/3

Polite Contradiction

It softens the impact when you are about to contradict someone or something.

I must say, I see things quite differently.

Pro Tip 3/3

Mild Surprise

Use it to express a gentle or polite surprise about a situation or fact.

I must say, I didn't expect such a warm welcome.