On the chainsaw board I hang out on, even the Stihl guys don't recommend the trimmers. Names for trimmers are Echo, Shindaiwa, RedMax. I personally have a Shindaiwa trimmer and I have to clear a lot of irrigation ditch with it. I fill the tank and run it empty wide open the full time. I also put a blade on it and go clearing thick weeds and saplings. Its the 272T model.
Shindaiwa | Products | Trimmers & Brushcutters | T272 & T272X
I also used to have an 039 farm boss saw that I couldn't get to run very well. (yea I know its a lower end one.) It would run for a bit and then start to bog. I tried to take the saw in for warranty work and the dealer would let it idle for about 3 min and then tell me it was fine and they couldn't find the problem.
I had a buddy who bought a 044 with a 20 inch blade and had the oiler turned up all of the way and it burned up the bar because almost no oil would come out. He took it back to the dealer and they said they fixed the oiler but not before he had to take it to the western USA manager to get them to fix it under warranty. (Saw had 30 min of cutting on it one week after he bought it.) It still doesn't oil right.
Around here, I have found that the Stihl setup quality is not the best, but the worst part are the dealers who think they are high and mighty and can't be bothered to talk to you after you leave the store with your new product.
I got rid of my 039, stopped messing around and bought a Husky 372 with a 24 inch bar and have loved it ever since. When I go in for normal wear items (saw has run great and not needed any kind of work so far.) the dealer is always happy to see me and is just as eager to help me with a 50 dollar item as he is a 1 cent item.
I know some think that Stihl are the best products in the world and that is fine, its just my personal experience that there seems to be a lot of issues.