Wayne-
It might be a 'fine' engine, but not fine to work on. I've worked on a lot of small engines...that twin briggs is the biggest PITA out of any of them to work on. The carb is unnecessarily complex and if you want to clean/rebuild it the right way (as in completely) you have to remove it (and the intake manifold) from the tractor. In fact, to access almost anything on the top of the engine, you have to remove the carb and manifold. The breather assemblies are serviced as a unit and do not have replaceable parts. Briggs made everything such that you have to make a bunch of special tools to fix parts of it. To get at most parts of the engine, several tight, ill-fitting shields must be removed, and if you want the flywheel shroud off, the engine must be pulled. The charging system is a bit anemic, and the starter is not only less fun to remove than a KT-17/M18 starter, it has several plastic pieces and several large vent holes that allow it to collect massive amounts of dirt and junk that make it get really noisy.
I don't want to sound like I'm relentlessly bashing this engine, but after having one and having experienced all of these things...I'm not impressed. There easier to fix, more thought-out engines out there, that's for sure.