I have had a Stihl FS90 for the last three years and it has been great. I have all the attachments for it except the bed definer/edger. I do that by hand. The powerhead has plenty of guts to take on any job. I use it nearly every day either for hedge trimming or for limbing up trees. Its tough to beat, I would like to get a second one to keep the guys and I moving. We use the grass trimmer attachment but a dedicated trimmer is much preferred. The unit isn't as balanced as dedicated trimmers, the trimmer shield is too big and the clippings clump often. Also the head isn't half as easy to string as my Red Max's are. Cold start up is easy but after years and hundreds of hours of use it doesn't like to start up when super hot.
I think you'll find that once you buy it, you will have more and more reasons to use it. Its what happened to me haha