I've considered trying Max/MSP at some point (in fact I think there was a forum topic about this years ago), especially since Cycling74 has been bugging me to buy it ever since I bought some other product from them, but I always feel like it would involve taking on a huge, new learning project. Wouldn't mind seeing a demo of "Max for Live" but I don't think the integration would really be a big selling point for me. It seems like Live and Max/MSP are sort of opposite ends of the music application spectrum. One is a "sit down and start tinkering and within 3 minutes you're making something that sounds cool," and one of them is more "lock yourself in a room with a pot of coffee and a manual and a computer for a weekend and you'll start to figure out what the program is capable of doing... and you might actually do some cool things with it after another month or so."
Also I'm still using Live 6 and I'm fine with it.