Shaymin has caused me the most problems, without a doubt. I've swapped my Mismagius out for a bulky Crobat and I also run CB Arcanine, but it has still caused me significant problems as it is a nightmare to switch into and is really hard to kill once actually in play. Staraptor is worryingly common but I haven't had any problems with it; then again I do use Steelix so I haven't got that much to fear. Agreeing that SR is a huge advantage in the current metagame; more people should use it as it keeps quite a lot of the dominant threats of the metagame in check. Registeel is amazingly popular, but doesn't really ever seem to do much; it's weak offense stops it from being really threating imo. I would imagine this will fall with use with time. Pretty much everything is carrying Toxic at the moment as well, which is annoying when your ReSTalker is down on bulky offensive teams.