Rock solid is relative. The FiTech is still too new to give it long term reviews. And the factory stuff was great in it's factory setting, but once you take a well-used one from the junkyard of unkown condition and add it to an Early Bronco with a piss-poor electrical system, there are just as many, if not more teething problems with factory EFI as there are with aftermarket.
I'm just not sure we can say how durable the FiTech unit is yet, since it's just not that old. I don't know when the first one was installed, so can't say for sure. But don't think it's been on the market more than a year yet. Or if so, at least not much more.
The components are the tried-and-true GM based sensors, injectors and such, but the physical stuff it's bolted to is all fairly new to the world. And installing them in EB's even newer.
So durable is yet to be seen maybe, but so far, so good.
No more trouble getting them up and running than Frankensteining a factory setup into a Bronco. Probably less in most cases.
Still plenty of issues installing FiTech and others too, but about 80% of those end up being something wrong with the Bronco's wiring. Not the fuel injection.
The jury's still out on the issues that do end up being related to the product. Most that I remember have already been dealt with by FiTech I think.
Paul