Extractions are extremely strong, but also very vulnerable. Originally, with three Extractions, they always got stuck. With two, I was happy. Alas, Extraction does nothing to improve a board position against aggro decks, so I went down to one (and I would have loved a second one in the SB). Having it maindeck is very, very good. It usually takes opponents by surprise, you rarely miss, and it gives you a huge information advantage in the second/third game.
Only one "blind" Extraction I played missed completely all weekend. Don't hold on too long to them. Extracting right when the midgame starts is a powerful play, putting you ahead. But remember that although solid, Extraction does not win the game for you (except against some combo decks). It's often better to take out support cards that you know will be in there (Ritual, FoW, Drain, Duress, AK's etc.) instead of gunning for the win condition which might not be only one card.
For example, in my quarterfinal match vs. Tog I extracted FoWs first, and replaying it with Will I took AKs. Naming "Psychatog" for the first one would not have been a good move, since he had Tinker/Colossus as backup. If you want to go for a win condition, do it only when you know that one Extraction gets them all.
I digress... however, maindecking one Extraction (or two, if you can support it) is very solid. Right now I prefer Extraction over Mind Twist (which you might have noticed is not in the list), because it evades graveyard recursion and Welder tricks. It also gets about the same number of cards as a Mind Twist for 3, sometimes more.
Also do you consider this deck on the same level (or close) to any of the other viable options for control decks?
Well, what are the viable options? Basically, Control Slaver and Mono-U. I made the deck to get away from 4CC. Control Slaver is stronger than this deck, Mono-U is about the same but worse in a random or aggro metagame.
Dozer