i actually used one for over a year in heavy comercial use. all i did was clean the spark plug one time, and the spark arrester has never been cleaned. i don't know about the newer epa regulated units though.
Ive had a 2100, which is the same thing, and used it regularly for 3 years now. I also have a 2400 and to be honest with you, there isnt any noticeable difference in power. The 2100 is also lighter. Everyone always seems to grab the Echos before they grab the Sthil Fs85. The sthil seems like a lead weight compared to the Echos. Although I personally feel like the Stihl has more power. Still the 210 is a good trimmer, especially for light use.
i actually used one commercially for two years. i bought it in a pinch, expecting to replace it, but it just keep on running. finally got tired of it's slouchy power and bought a 260s. but the old 210 still runs. you can pull start it with sewing thread now it's so worn out, but it really never lost much power it seems.