Okay, I got reqs on OU Current, so I'll share my experiences facing Keldeo.
Well, unfortunately, I didn't actually see a lot of it. I played roughly 60 battles, and saw it in about 10 of them though. I'll admit, Keldeo is a monster. It can be difficult to stop, and was the cause of a couple of my losses. Despite this, I don't think it's broken. I was able to combat it and defeat it in most cases through smart switching and preserving my (admittedly flimsy -- I ran HO) checks. It wasn't getting around these checks with such ease that I am convinced it is broken. I had a Starmie, which is OHKOed by Specs Hydro Pump and a Dragonite, which also is OHKOed by Specs Hydro Pump (after Stealth Rock damage). Specs was however the easiest to play around -- its Speed was middling enough for me to revenge it with either my Scarfer or Starmie. Scarf ended some games against me, and was difficult to beat -- I consider it the most suspect-worthy set. Expert Belt was really manageable, being weaker than Specs, which makes it much easier to handle. Scarf is fast and an adept revenge killer and cleaner. It still could be checked, but against my team, it was by far the most threatening of the Keldeo sets.
My conclusion is that it's not broken from the metagame with it. I ran a fairly Keldeo weak team and still managed to beat it in most cases. It might just be the ladder quality -- I don't really know. In my experience, Keldeo was not an overwhelmingly powerful threat that could smash apart everything and was impossible to play against. I'll see what I think of the metagame without it.
This is just my opinion based on what I saw, and could very well be flawed in the grand scheme of things. I really don't provide an argument for Keldeo not being broken other than how I handled it on the ladder, my battles on which are of course different than those of everyone else and thus have little value in an argument. I'm not interested in one.