I know Hamilton will be the first here with one and I'll be waiting for the "Hamilton" review. I'm the same way, I had the greasy D600 but find that I much more enjoy shooting with the smaller cameras. They're just plain fun. If the A7 its really under $2K with the kit lens, I might sell off some gear to try it. I don't want the 36mp.
Supposedly, the cheaper one also has phase detect AF. It sounds like the cheaper may be the better camera...
I'm too invested in a-mount glass on a limited budget to really consider switching. Though Sony may not give me a choice if they kill off the a-mount some day.