I've never had any trouble with my cheap weedeaters over the years, and I cut 1-1/2 acres. The problem is with the head/spool! I started using the kind of spool that takes individual cut pieces of line and that works a lot better than the old continuous feed models.
+1 on Echo - I started mine for the first time this year today; probably had to pull the rope three or four times. Haven't had a Stihl trimmer, but I have two Stihl chain saws that are super!
Stihl all the way. Trimmer, blower, chainsaw. Stay away from ethanol gas and it will last a long time. Maintain 2.5 acres and my equipment gets a lot of use for a homeowner. Not to mention my local Stihl dealers service is second to none.
Worx 24V 12" Cordless Grass Trimmer WG166.
You also get free cord for life of the trimmer.
I am still on the 4th of six rolls and it starting the 3rd year of use.