I've always found Matt's "MLS Watch" posts over at really interesting.
shows 36 active listings at 2200, and 65 at Cosmopolitan (along with a picture that very much reminds me of the )
It's also been noted that a quick search of craigslist yields several rentals available at each building as well. Cosmo comes up with 29 results, though I'm sure some of those are duplicates. Cosmo is quite a big building, but 65 listings+several rentals seems like quite a lot.