I spoke with the layout guy today, and I've once again had to re-evaluate my understanding. Seems like gates don't propagate metastability. Since gates are railed to VCC and GND, and they don't have internal feedback like flip-flops, metastability is unlikely to propagate through them. This includes regular gates, and buffers, and I'm sure other stuff too.
This means that metastable oscillation is pretty unlikely. Unless of course the output of one flip flop is tied back to its input without going through buffers, or gates.
I guess the only likely issue with metastable flops is the uncertainty of the output. Oh well. I'd still be careful.