We weren't flight-critical so we could fail hard and reboot it if things got messy. I would guess B don't have that option so god only knows how they are planning to deal with disagreement between each side of the system during normal operations, dual systems can't do majority voting :-). As a result, I would expect a number of new issues to be found in the system for some time after it has come back into service.
One of the issues I would have thought is that the computing hardware stays the same but they are asking more and more of it in terms of workload. I doubt that this was allowed for in the original specification so forcing something that was primarily designed for navigation and performance to take over critical flight control function *and* monitoring seems like a bit of a step. Do the FMCs run a RTOS?