I like the trimmer as a whole.
It's very light, easy, accurate, BUT if your grass meets the wall you're going to run through those blades like there's no tomorrow.
I'm being very careful not to touch the wall where I can but if you want to actually cut the grass against the wall, you just can't help touching it occasionally. The plastic blades wear down so fast that I go through one every time I use it. There's about 15 meters of rendered retaining wall that I just have to trim against and really wish they used a normal line so that it keeps extending as it wears. I think buying the blades will end up more expensive than the unit itself.