SP decks are extremely fast, and can be extremely annoying, especially with Dialga G...being that the majority of them will be using mainly only SP pokemon, it makes for alot of room that can be used in deck building, a good SP deck should never have a problem with not getting basics on 1st turn
poke-blowers are a good counter to pull Dialga G to the front to kill it, but there are way more ways to get them back out...I've got a decent counter for SP decks, but it's a matter of not getting horrible draws and/or out-speeding their SP deck
Machamp requires field manipulation to take out the SP's that aren't protected, either by their own poke-bodies or Unown G...Poke-Blowers, Cyclone Energies, Warp Points, Palkia Lv. X, etc.
Gengar is really iffy...I haven't come across a Gengar deck yet (speed or otherwise) that can beat my AMU rogue consistently enough, and while Gastly free attack is a good way to slow SP decks among others, it won't stop them cold
Mightyena (LA) is a good pokemon to use against SP decks, because it stops unevolved actives in their tracks
Mewtwo Lv. X is another that requires field manipulation to make sure Dialga G doesn't stop it
it's all a matter of being able to stop them from using the supporting cards in the deck and out-speeding them...if you don't, you lose...there are counters to the decks, but there are currently many ways to stop the counters, and being most of the Platinum sets will be adding more and more SP pokemon to the format, it's only gonna get worse