In my almost five years living in Rome, with all the events and liturgies I've been to, I've seen this habit only once (got to be a seminarian).
At the same time, after almost five years, I've seen the Carmelite habit only twice, on Latin Americans. I've never seen the Teatini habit and I've only seen the Trinitarian habit perhaps twice, on what I think to have been the same guy.
I've seen the Jesuit habit a few times, the Oratorian habit at the Chiesa Nuova (or Palazzo Massimo once a year!) and now we see again the lovely habit of the Augustinian Canons of Stift Klosterneuburg as they have a few studying in Rome.
But, there is hope. In fact, the one and only habit that one most often sees on the streets of Rome, at Rome's airports and her train stations and at papal events, is that of the Legionaries of Christ.