Full disclosure, I'm a dealer for AMSOIL products, but I also use AMSOIL Saber at 80:1 with high octane fuel (91 or 93 depending on the gas station) in my saws, including modified saws that I've built (woods port, gasket delete). Not trying to convert anyone, but I've had good success with it and no oil related issues with my saws to date. They have done a lot of testing on it with trimmers, but I do wish they would do one with chainsaws due to the differences in RPM's and load between the types of equipment.
The mix ratio can definitely alter your engine's performance and carb settings. If your saw is tuned from the factory to 50:1 and you put 40:1 because you think more oil is better, you may run the risk of leaning the saw out because you have less fuel per volume at a 40:1 ratio.