I heard it's a 5 hour game.
I've also heard it's an 8 hour game, and a 12 hour game, and a 15 hour game. It depends on who you talk to. Suffice it to say that 5.5 hour completion time you see quoted everywhere is from a Youtube speedrunner who skipped all skippable story content and did no exploration. They just ran through the levels without dying. The typical timeframe for people who actually play through the game normally seems to be about 8 hours or so, which is fine by me.
Honestly, the complaints over completion time have to be some of the most idiotic I've seen in a while. It's like the internet was experiencing a shortage of things to bitch about. So long as you find the experience enjoyable and worth your time, I don't think the completion time altogether matters. It's especially hilarious seeing the press jump onboard this gravy train considering so many of them
also bitched about Alien Isolation being
TOO LONG at 12-15 hours last October.
As for that speedrunner, I think uploading an
entire game to youtube before the game's even
out is a particularly dickish thing to do. I hear Sony took the videos down, and I can't say I blame them.