It's the most interesting for me. With the announcement of A7 II, I think I will now wait for the updated version of the A7s, though. Unless the price of the current model takes a massive preemptive hit.
Well, I think the A7sII will be a while since the "s" isn't that old yet.
I rented all three, but unfortunately not at the same time to make comparison easy. The "r" files are indeed huge, and not sure really need that. I'm not sure how or why, but it just seemed as if I was happier with the results of the "s" than the others, and it did seem the shutter wasn't as loud (of course had the silent mode, under special circumstances.)
Rumor has it the "A9" will be a pro model to compete with high end Canon/Nikon: read, will be expensive. Something should be announced Jan/Feb of 2015.
I've been slowly going through a small stockpile of film I have, so haven't been sweating it. However, I must admit to being tempted to just pre-order the A7m2. I definitely like the improved ergonomics, which I think will make my largish hands happier. Sounds like it'll be a bit faster, which is always good. It would be nice, with the bigger body bulk and better dust/water protection, if the shutter is at least a tad quieter. Anyway, for all that it has, price isn't too bad. The "s", however, is still pretty expensive.