Since I've been a home owner I've had a Ryobi with a few attachments, and a Troybilt 4stroke ( which happen to allow the same attachments ) and am currently using a Stihl ( it had problems in the beginning, eating string, this has been somewhat cured )
The Ryobi worked ok the first few years, then the hoses and primer bulb rotted, replaced those and it didn't really run right after that, I suspect a piece of plastic or rubber from bulb or hose got in the carb
The Troybilt worked, it was a 4stroke, it didn't spin like the 2stroke, and didn't have the knockdown the 2stroke had. forgot to treat the fuel and fubared the carb.
The Stihl FS 56RC I currenly it's a power house, it's just under the commercial grade. when I first got it it would eat the string off, tried several different sizes and types, I got pretty frustrated as I'd have to rethread the string every few feet especially in heavy or tall growth. , finally the Oregon Gatorline Magnum .105" square line has been the best performing, longest lasting. ( I buy the one pound donut and that will last a little more than a season )
Trimmer works well, easy start. My only complaint is the same I've ever had with any trimmer, they are made for SHORT PEOPLE !! another foot or so of driveshaft and it would be comfortable for me to operate for a good amount of time. Currently I have to hunch over and my back starts killing me after about 20-30 min. ( the shoulder strap isn't long enough to drop down any lower ) I should have paid up and got the FS-56C, it has handle bars and throttle mounted on the right grip