Late to the party but I think you made a good choice. I use a similiar Stihl unit to do my pond and it works great. Took a 2 hour weed wacker job down to a 30 minute job. You are also correct that it is nice to have the grass lay down in place instead of the week wacker throwing it into the pond.
Glad to hear that!
I'll give the trimmer a try in the next week or so. The trimmer I purchased is a little heavier than a weed wacker but the speed at which it cuts should make up for the additional weight. I got to test it on some weeds today and that thing flies through some tough stuff. Definitely much faster than a weed wacker.