I've burned through more sets of these tires than i care to think about. I got my first set back when they had the yellow side-knobs because i thought it would look cool on my Yeti (they did). These things roll so fast and spin up way quick because they weigh very little (450gr for the 2.1s). They're not super aggressive, but when they let go they do so very predictably and they're really easy to get back on track.
They can be found for 12 or 15 bucks if you keep your eyes peeled which is what gives them an edge against their only stiff competition, Schwalbe Racing Ralphs. Those mo-fos are like 75 a pop and don't really out-perform Pythons save for having a softer casing, which you'll only feel under 28psi or so.