I've used one for about 3 yrs now, and have had ZERO problems. I've used Stihl HP Ultra oil & 100% gasoline/89 octane mixture at 50:1. Just started it up after sitting for a couple of months during the winter and it fired right up. I clean the air filter once a year and clean it a couple of times a year and it just works. I've only got 2 attachments; the trimmer & the brush cutter.
Pros: light weight, reliable.
2009 Nissan Titan pullling a 18 ft PJ Trailer
2011 Kubota ZD326S (60") - 26HP Kubota Diesel
2010 Bob-Cat FastCat Pro 48" w/Accelerator (20HP Kawa)
Non-commercial 21" walk-behind
Blowers (Stihl BG85/Husqvarna 170BT)
Trimmers (Stihl KM110 & FS90, Kawa Multi-Tool)
Chainsaws (Stihl MS180 & MS362 w/20 & 24" bars)
& misc hand tools & equipment