I just cut through a 6x6 pressure treated beam with my Ryobi brushless circular saw. Didn't even bother to upgrade to a diablo blade. And it worked great!
I made six more similar cuts. No problem.
If I was doing this every day, would I upgrade to Milwaukee? Probably. (More than likely buy a corded saw.) But for weekend home improvement projects, don't doubt the power!
That's another reason I like the Ryobi lineup. I started out with one of their basic drill combos.
But as I pickup bigger and bigger projects, I can upgrade to their Brushless and HP models, still using the same battery.