ResTalk (Curse) Registeel is really good - players are just expecting it to roll over and die but with recovery it can check more for longer.
It actually is a huge threat right now, and can sweep an unprepared team. I run CM Slowbro or Encore Poliwrath to stop it. Both can switch into Iron Head and set up freely.
Scyther is pretty good. It's like a Swellow that's quad-weak to Rocks, has a better set of resistances and lasts longer but doesn't hit as hard.
curse registeel doesn´t have a lot of pp on any attack aside from iron head, haze milo can probably stall it out, still you can really easily sweep an unprepared team but any team that took it into account while it was being built will either remove the boosts or force it out easily
On the topic of Encore, Encoring Poliwrath has got to be the Breloom of the UU metagame. Come into one of its many resistances, Encore it, set up a Sub and start Focus Punching. It's probably one of the best Rain counters ever, provided that you let something else take care of Ludicolo.
EDIT: Damn, ninja'd by Dan Dan
What i meant is not that you shouldn´t run iron head, since it is the best move for curse regi but i meant that, aside from it registeel doesn´t have too much pp on any other move, it can be stalled out of it by a haze milotic if you have a big weakness to it in your team. And yeah pretty much every team has a milotic, just sacrifice ice beam or toxic and there you go. Having no way to counter curse regi is a big problem since he can kill all your team if you don´t act fast. Also i face curse regis almost exclusively :PHaze Milo can but the thing is, Unless it's a Life Orb version, it's not killing Registeel anytime soon unless you get crazy lucky with crits. And why wouldn't you use Iron Head? Putting EQ over Sleep talk makes him set up bait when using Rest so Iron Head is the move you should expect. And not every team wants to put a Hazer on there team because they don't need it and to force him out, you need to get in strong Physical attackers with stab Super effective moves before a couple Curses or he's just going to Rest off the damage, or you will need Strong Special attackers with either STAB on super effective moves, set up moves, or very high Special attack. And no one accounts for Curse Registeel since there nearly all just the ones with Stealth Rock/ Twave/ 2 other moves.
Edit: Why did I never see any Curse Registeels before for that matter?
What i meant is not that you shouldn´t run iron head, since it is the best move for curse regi but i meant that, aside from it registeel doesn´t have too much pp on any other move, it can be stalled out of it by a haze milotic if you have a big weakness to it in your team. And yeah pretty much every team has a milotic, just sacrifice ice beam or toxic and there you go. Having no way to counter curse regi is a big problem since he can kill all your team if you don´t act fast. Also i face curse regis almost exclusively :P
Curse Registeel is really overrated IMO. It is so easy to play around it. I mean, how much of a threat is CroCune in OU?? Not much. I'd be more scared of CM + 3 Attacks Cune than Crocune. Same as Registeel. I'd be more annoying if it had something like Thunder Wave, Stealth Rock and general annoying moves than a sweeper.