I like mirror blackout. Lets me know something's going on.
I don't have many, if any, shots where the subject is blinking. And, a blink is so quick anyway, that i'm not sure i would be certain if i had caught the blink even with a rangefinder.
Since my first cameras were SLRs, mirror blackout is the standard. I'd miss it if they developed an SLR without it. I read a rumor that Canon's working on a dSLR with no moving mirror..... It's kinda like the shutter sound. If they made a dSLR with an electronic shutter, so that it made no noise whatsoever, they'd probably add some sort of sound effect just to keep people 'comfortable.' If i'm using my CM or T3 in a noisy environment, i hate having to look at the exposure counter to see if i actually just exposed a frame....
I especially like the mirror/shutter sounds and blackout on certain cameras. Contax Aria, Nikon F80, Nikon FE2, for example. But, the shutter and blackout on my Leica R7 seem very slow in comparison.
How about the blackout on a Hasselblad 500? The mirror doesn't even return until the film is advanced.