While I've had excellent results over the years with POR-15 itself,
the two Restomotive products I have been somewhat disappointed by were:
1) Their gray exhaust coating, which began burning off at the head end of
girlfriend's Volvo exhaust manifold after a few months.
2) Their epoxy putty in metal repair situations. I found it to shrink and
crack a bit and cause the rust to come back in the resulting crevices.  That
said, it works great for repairing plastic parts.
I'm pretty diligent at following their instructions, but your results may
vary.

-chris