II've had a little Stihl before my 34 year old son, all that has gone wrong with it is the shut off switch failed after a couple of years, I have choked it off for decades. I hadn't used it for at least 5 years until the other day when my son needed help with a big old black locust. We drug the saw out, filled it with clean fuel and lube and damned if it didn't fire off after a dozen pulls. It has cut dozens of cords of wood and helped fall and clear a good acre of odd sized trees and even brush one year. Mine is one of the first years of electronic ignition, the best thing that ever happened to this stuff.
If I needed to replace it I would with another Stihl, probably something on the order of a Farm Boss or similar model, try to get at least a 20" bar.
Another saw I've used while at work was a Big Husky 460 I think...it was a real animal, I loved it...it could tip cut stuff that another saw would stuggle with, never bogged down on anything I cut. We had quite a bit of overgrown hardwoods, like ornamental cherry, apple and plum and that thing ate everything like butta. Those are two I'd recommend, Stihl and Husky. I have a full compliment of Stihl yard tools, edgers, hedge trimmers, blowers...don't use anything less and never have problems. Keep your fuel stabilized and mixed perfectly and you'll never have problems with it.