Recent all seasons, are not bad at all under all conditions but never stellar either. On the other hand, when you can go for a summer performance tire, I'd assume that those recent Michelins, Pirellis and Contis are beyond believe! The M3 RWD performance on Michelins I drove a month back really astonished me!
I have early experience on runflats and on my e90 it was really pure trash. On my e91 it was already vastly improved. But afterall, it's still a compromise that deminishes the dynamic (and comfort) capabilities in favor of being able "to run flat". On a M240i, I'd go for the non run flats and premium summer tires. The car is probably worth it!
