I have shot about 500 silent pictures (simple mode) on past few days. Some of those have been captured with intervalometer (1, 5 & 15 sec) and for some I have manually halfpressed the shutter button.
After moving files to computer I noticed there's completely black frames every now and then, also some frames with only a bit of green there and here.
Otherwise silent dng @ 1-2 mpx is really, really great! Fullres not necessary for me, anyway the end product is video at maximum of 1920x1080.
ML nightly Aug 01. 5d2 & Sandisk Extreme 16 gb 60MB/s. 550d with same days nigthly no problems (shot over 5000 frames).