Any ONE person with a bad experience with their ELS, which has likely happened, COULD give you a warning about the ELS series of engines but what would that persuade you to do? A person with a bad experience is 10x more likely to share it than a person with a good experience, that is unless they are being coerced into giving feedback.
If what the others are saying is true, the ELS is neither the best, not the worst engine that Briggs has made. The ELS is certainly not to the quality and performance of a Vanguard series engine but it isn't their worst engine either.
All the same things could be said for Kohler as well. Courage, not the best, 7000 series, arguably better, Command Pro, better than the others?
I don't have the specs or copious amounts of data to "prove" the ELS to be either great or terrible, but I did own one and short of a fuel related carb issue and a governor that I broke by mistake (fiddling with governor arm during full throttle), the engine ran smooth and had plenty of power. When I got rid of my Cub for my Exmark, the mower had almost 300 hours and it was running perfectly.
At the end of the day you just gotta go with your gut and should you decide to embark on this journey set a limit for when you call it a quits; just in case the problems get too costly.