This may be new, but it now shows up when you click on the "My Hotel Stays" link in the left-side navigation.

When the list of hotel stays comes up, at the top is:
You have 31 stays at 6 hotels for the past 12 months or whatever you count is.

Yeah, I know, I'm an amateur at that low a count

Don't know where it would show nights, you may have to count them up.