Finally got the fast cards! I can report that I am getting 1280x720@24fps continuous RAW using SanDisk Extreme Pro 95 MB/s card. This occurs after about 15-45 seconds of recording with a write speed of 36.9 MB/s and idle time reaching over 200ms after a few minutes and then slightly over 300ms thereafter. Not sure how much format allocation unit size matters, but setting between 64KB-128KB seemed to work best.
Recorded for about 11.5 mins with file size of 25.7 GB on a 32 GB card when it shut down automatically (on its own).
One thing to note, in the past when I set the fps override to 24fps it would display actual fps of 23.973, now when I set it to 24fps it states an actual frame rate of 24.002, so I don't know what's up with that.
UPDATE Dec-14-2013: Using the latest nightly build (Dec-13-2013) the actuall fps is back to 23.973 (whether setting Desired fps to 24.000 or 23.976), so I guess that's good.
Also, on a side note related to the new MLV raw video format, on the 650D .mlv is a little slower than .raw recordings, to the point that it won't record continuously for 1280x720p @ 24fps, I can see the MB/s slow down jnto the low 36.x MB/s when in MLV recording mode, all else being equal.