First of all, I'm an idiot.. Yes, if you press (or doubleclick) on the contact you wish to see more details on, it'll tell you which number was used and the time and date the call was made, received or missed.

Got too obsessed about the way Conversations works that I didn't remember about it -- had been using it for a while now, though, so yeah, I'm dense.

One thing, though, and I don't know if the poster you replied to was referring to this (as opposed to the time and date when a call was placed): is it possible to know the call's duration? I mean, for received and (especially) outgoing calls, of course. Don't know if the system stores this info too..