Basically every two-cycle engine manufacturer that makes weedwackers makes a modified unit with a vertically mounted blade, a shield, and some sort of wheel or guide. You can basically take your pick from Stihl, Echo, tanaka, redmax, husqvarna, etc, etc. If you're not partial to any brand, you might consider either waiting for people to weigh in here, or going to lawnsite.com and trying to get the opinions of some professionals.

Do you currently own any sort of weedwacker? A lot of guys, even professionals who do a lot of this work, just choose to hold a straight shaft weedwacker vertically, and use this to do the edging. This would probably be difficult the first time if your edges are that overgrown, however, if the string trimmer method is used weekly or every two weeks, it works just fine. So if you don't currently own a string trimmer, or would consider upgrading your unit to a straight shaft model, you may wish to do that, and then have only one machine.

One last thought--if you have any interest in both a dedicated weedwacker and or a dedicated edger, you can get both machines in one, through the use of a kombimotor or split shaft tool carrier unit. Stihl, Echo and Redmax all make this--it's a powerhead that can then accept attachments (weedwacker, edger, rubber debris broom, hedge trimmer, etc).

MGF

McClane or Scag.

I've never seen one of these in person, but this looks intriguing for a new walk behind.

Tanaka TLE-600

Here is a link that might be useful: Tanaka Walk-behind edger

Thanks for the input. I've currently got a Shindaiwa 22t straight shaft string trimmer. It's quite a pain to use for edging given the amount of edging I have. As a result, I probably only edge 2-3 times a year. I'm looking for something easier that gives a more finished edge.

The Tanaka looks like an interesting machine, but it appears to sell for $700+, which is way more than I want to spend. I'd go up to $400-500, but even that could be a hard sell for my wife...

http://www.lawnsite.com/showthread.php?t=158741

There seems to be strong support for several Stihl, Shindaiwa and Echo models.