I agree. Having a few questions in mind is always a good idea, though I tend to prefer discussion starters rather than a simple, straightforward question. It gives you the opportunity of a follow-up, which let's you talk about a topic of _your_ choosing. My usual rule of thumb for end-of-interview discussions is that it should last until the interviewer suddenly realizes time's up. Then you know that they really enjoyed the conversation.

In general though, I'd avoid HR-related questions. They are almost always likely to generate a generic response, almost every candidate will ask similar questions, and they can easily be answered by your HR department contact.