gas powered echo straight shaft will last a homeowner a long, long time. My former next door neighbor was a gardener...he bought the homeowner grade echos at home depot and they lasted him a year, doing about 150 lawns per week.
Depending on your yard size - you might consider battery power. I have the Black and Decker 18 volt weedeater. It is good for 15 minutes per battery and no gas or cord. If I had to replace it I would get gas - I used to drag cords all over the yard and hated it.
Echo what others have said. Save yourself a lot of frustration and get the Echo or Still. As an old fart who has gone through a gillion edgers trying to get the bargain I finally bought an echo and it has lasted 4 yrs and still going strong. Just be meticulous when you wind the string, you will be grateful for it and love the dependability of the higher grade system.
Hookem
I went out and bought a Black & Decker rechargeable weed eater - I think its called the Hedge Hog.. I have a modest sized lawn and it works great The current one is my second one...the first lasted 3 summers. It costs $90.
Black and Decker grass hog. no mix to mess with and it's a lot quieter, lighter, and still very powerful. the handy dandy guide is nice too. really no reason for gas unless you need more than 2 extension cords to reach every part of your yard.
however, if must have a gas powered then Echo or Stihl are your only choices. I had a Homelite and regretted every minute of it. it worked ok but the string advance was crap and underpowered.
I have the cordless 18V Grass Hog and it works great. I can weed eat the entire yard on one charge. It's super light also.
I also have the Black & Decker cordless 18V leaf blower and it uses the same battery. I need 2 batteries to do the job (weed eat and blow) but works great.