So I redid all tests at 1024, but with AA mode Quincunx activated.
After running the demos with Quincunx, I charted the results from best to lowest score. This is the result (attention : the bottom level is 60fps, not 0fps) :
As before, there is an important performance hit, yet we are talking about scores that drop from over 200 to around 150 on average. As before, Quincunx levels out the performance jumps and makes the average framerate smoother. The heaviest maps are still Crusher and Torture1, but even for them the average performance maintains itself comfortably above the critical 60fps limit. It seems obvious that, in all but the heaviest maps, Quincunx is quite a playable alternative.
That being said, this chart outlines the average framerate, not the minimum framerate. If, without AA, the framerates never stutter, with Quincunx activated maps such as Torture1 (arguably an over-the-top example) really bring the system to its knees. I will have to try that demo without the timedemo parameter activated to check if any framerate stutter occurs.