PT, the PlayStation 4’s demo for the upcoming Silent Hill game first revealed at Gamescom, has been downloaded over a million times, Sony revealed at its pre-TGS press conference.

Of course, part of the mystery of PT, at least initially, was that it was randomly uploaded to PSN during Sony's Gamescom press conference, though it wasn't clear that it had anything to do with Silent Hill (or Hills, plural, as the title of Kojima's upcoming says). Its popularity likely ramped up when everyone heard about its Silent Hill connection, as well as the fact that that Guillermo del Toro is collaborating with Kojima on the project.

The other interesting feature of PT is that it's incredibly difficult. Notoriously so, even. If you're having trouble with that infamous final puzzle, in particular,we may be able to help you out. In the meantime, steel yourself, because Hideo Kojima wants you to **** your pants while playing Silent Hills. You've been warned.

http://www.ign.com/articles/2014/09/01/playstation-4s-pt-silent-hills-demo-downloaded-1-million-times

Looks like this game could reinvigorate the Silent Hill game sales.

Is it PS4 exclusive?

The demo/teaser/whatever is.  No wording on the final game yet though

The Demo is exclusive on PS4, I think nobody really knows if the final game Silent Hills will be only on PS4 or also PC and/or XBO. Sony didn't say that it will be exclusive so probably not but maybe even Kojima doesn't know yet if he wants to release it only on PS4 or not. 

@topic, yeah that's why I said some days ago that I think we get many horror games lately (especially from smaller devs) because Let's Players are able to push sales a lot and Let's Players play these games a lot because fans of them love to watch how they play horror games.

I'm sure many of these downloads came from people who saw a Let's Player playing it. 

Wouldn't count on it, but it probably is in JP.