I have this saw, I use it for felling cottonwoods. It's a SOB to change bars and chains, I have a 20" and a 27" bar. I bought it from a tree care guy who had it for a backup felling saw, almost new for $200 cash.
A few weeks ago we dropped a three foot thick dead cottonwood and my buddy used it to cut his 360 out, his wedge slipped. His superior attitude changed as soon as he laid the 670 into the stinky cottonwood. Surprised the heck out of him.
I know that folks here despise Echos, but this saw is great for the half dozen big cottonwoods that I drop and buck yearly, a farm tool. No problems in 6 years, always starts quick and easily, I just use treated stihl mix and drain and fog the engine in the fall.