For me, heavy trimmers are only heavy for the first week or two, eventually you get used to the weight & plus the muscles your arms & shoulders get a little more cut & defined. I have used many, many string trimmers & this is what I've noticed.
If you're 170 lbs. or more, the weight of that tank may not bother you. But as they say in the world of chain saws, " 2-3 lbs. extra is ALOT when lugged all day, every day". Yes you may get used to it, & get forearms like Popeye. Just don't stick your new employee with it all day or he'll prob. quit after the 1st day
Just an update on the use of the Honda 4 Cycle line trimmer. Both my 15 year old son and I have been using it for the past month and we both agree that it is a great trimmer. The weight really doesn't effect either of us. The unit seems to be well balance and to top if off, the power is awesome. I must agree with TurfMaster that most of the time we don't even have to run it full throttle. Wouldn't hesitate at all buying another one.