Yes, the dialogue is a little awkward. They talk and reply a little fast, from what I remember, and I don't think it was just the dialogue script that was odd.
For example, the conversation is actually pretty natural when Yuuna walks in on the computer chick and Shinkurou. But after he says "she wasn't always like that" she leans in really oddly saying "Really?", and it just seems like a forced method of letting us know she's interested in him/developing a pattern of jealousy.
I don't really mind or care that much, though.