I think that's the question on everyone's mind. Having done a 30 minute mash myself, I found no differences in flavor (besides the different hop schedules) from an overnight mash to a 30 minute mash. Of course, these are two extremes, so... doesn't really give a true test.
That being said, both beers had a very similar grain bill, I actually got higher efficiency from the 30 min mash due to a better crush, and both attenuated at around 80%.
Head is the same, taste is the same (same being no off flavors/etc.), beer is great.
So, what are we missing out on by going shorter than 60 min? No one seems to know or, the right people haven't seen these threads.
But at the end of the day, I'm making great beer, in less time. For me, that's all that matters. I don't really care that some process may not be "finished" by the time I pull my bag, but what are the cons of this method if they are imperceptible (to me, at least)?
I'm going to keep experimenting with it, but I need to do a side-by-side and have my wife/a friend serve them to me blind for my own satisfaction at some point.