I learned in 3 days in a 1979 Jeep CJ-7 that popped out of gear, had no synchros, shift linkage made out of silly putty, and a loaded trailer, on steep and twisty dirt logging roads. I didn't drive a stick again for a couple years until I bought a Jetta for my girlfriend (which ended up being my car because she couldn't or wouldn't learn to drive it) and I was to the "not-thinking-about-it" point in less than a week, including driving it in San Francisco, which is nothing but super-steep hills. I was heel-and-toeing in a month. I'd credit my "quick" learning to that evil CJ-7, because it forced you to be really good or you'd put yourself in the ditch or over the cliff (which I thankfully avoided) or else you'd stall, roll back, and jackknife the trailer (which I didn't avoid). Even my uncle's 1950's Ford pickup is easier to drive than that Jeep. The first time I drove the Jetta (and again the first time I drove a stick Honda), I was like "wow, this is EASY!"
I'd love to drive an S2000. Sitting in showroom, the clutch and shift linkage felt sooooo good, and the pedals are simply perfect for heel-and-toeing.