I used a Greenworks 40V Lithium G-Max DigiPro strimmer, and it worked pretty well. A 2Ah battery lasted about 45 minutes. It came with a 4Ah battery - my in-laws also have a 20" twin blade mower, that came with a 2Ah and a 4Ah battery. The mover really needs four 4Ah batteries to be useful for their ~1/2 acre lawn; when the grass is long, anyway.
The shoulder strap is well balanced, and it has two speed ranges, with the trigger letting you vary the speed. The gear box gets warm, but not hot. I think reloading the string is fairly easy - much easier than the Stihl was. (The Stihl was destroyed in the house fire at my in-laws house.)
It was on sale at Amazon for $170 with the 4Ah battery and charger, which is only $47 more than the battery alone.