Yes, sadly. I can't remember the last time Firefox crashed on me prior to 57. I've lost count of the number of crashes/hangs since the update, but it's well into double figures by now. Whether it's Firefox itself or the handful of extensions I have installed, I can't tell for sure, but it's much worse here on a Windows box with more extensions installed than a Linux box with just a few. In any case, if the new runtime model is supposed to make things more robust then unfortunately my experience has been quite the opposite.

57 user on OpenBSD here. No extension installed (at least to my knowledge ;)), no crash to report. It has been a pretty smooth experience so far.