I have a battery powered black and decker, its actually not too bad. I have their battery powered chain-saw-on-a-stick, and chain-saw-loppers, and they all take the same batteries.
It is fine for cutting grass around trees, walls, etc. Thats what we use it for. Its not going to make you happy if you are trying to cut large weeds that have strong stalks, or if you are trying to trim 100 sq ft of grass you can't get with the mower. I have bigger 2 strokes for that.
What I like with the battery one, is its simple. Its always ready (we have a total of 4 batteries, with chargers, so we have a rack of them ready to go at any time), and if you realize you missed one tree, you grab it, buzz-buzz, and done. No having to fuel and warm up a gas whip.
Because its easy, my wife will take it and go do the trees when she feels like it, she would never use the gas whips.
Would be great for a normal city lot, or spot duty like we do. Mine is 6 years old, and works fine. I would guess there are newer ones with LiPo batteries that are lighter and better capacity than my old 18v NiCad model, but I don't tend to run out of battery with it.