Speaking from experience with other computerized fuel injection vehicles, Id say its very reliable. Certainly there will be some bugs to work out when adapting a setup from one vehicle to another, but even then I think there should be no problem as long as you do some homework and match some specs up. The way I think of it with adapting this 4.3L tbi setup to my 3.9L 235, how would the computer know that its not on its original home? Some of the input from the sensors might not be where they usually are at some times, but the computer, to some effect can adjust the outputs to change that. Of coarse if the computer has to start making huge changes to the outputs to where its getting to far from its comfort zone, it might throw a trouble code.
And also the thing with these computers, besides them (the earlier versions at least) being very basic, is if there is a problem, the computer will go into limp mode and using preset variables should work enough to get you home or to a garage. I would say sensors barely, if ever fail. The wiring can be a problem as the harness ages, and the problem is usually right at the connector as the wire gets brittle and breaks from vibrations and the connectors get corroded from not being completely sealed. Buying a new harness instead of using one from the donor, though pricey, can help avoid these problems.
