I have the ESM Skyraider and am very happy with it. The fit and finish were very good. Granted the instruction we're the best but if you are putting one of these planes together you should have some experience and it shouldn't be an issue.
As for this quote "I again would advise to stay away from them unless you have piloting skills to match their aerodynamics. " That basically applies to any of the warbirds out there, no matter who the manufacturer is.
As far as the Beaver is concerned, I've built 3 different Beavers, none of them ESM, and they all need a lot of nose weight added. If you want the scale looks, which means a stubby nose, you're going to need to add quite a bit of weight up front regardless of if it's made by ESM or someone else.