I bought STIHL Weed Whacker KM 55 RC two years ago. It is a neat, powerful tool, a bit on the pricy side, but STIHL is considered the best brand out there, and I did not want a cheap version that would not last me one season. I also purchased a rototiller attachment, so I have been using this weed wacker both to prepare soil and trim weeds.
The first season everything was fine, no complaints. The weed whacker worked very well, helping me to keep our yard neat. During the second season, however, it broke, and I had to take it to the shop & put a new carburator in. After this was done, the weed whacker worked fine.
This year - season 3 - I had pulled it out just a few days ago and tried using it, and it wouldn't work again. I took it to the shop, and this time they replaced the muffler / catalytic converner. The weed whacker works fine again, but I am not too happy with all these repairs that have cost me over $200.