Would edging really solve the problem of shabbiness?
Edging is generally used to control the spread of grass into flower beds. I would think that in your case that the edging would be a waste of money.
How about some low lying shrubs or evergreens that you can plant along the edge of the lawn and use a mulch cover below them out to where the lawn is cut to end.
While ferns are nice unless they are large species I would think that they really do not present a strong enough silouette to demarck a zone between lawn and woods.
got some pics of the woods, of the ferns, of some low shrubs, or low evergreens. You could cut out the images of the shrubs and the evergreens and the ferns and lay them over the area of the picture of the woods and lawn you would want them and see how they compare?

or you could go with a natural rock edge....

I think that one of the best ways to make a garden look less shabby is to mow the lawn and carefully keep the edges trimmed. I don't think it is necessary to use any material as edging, just decide where you want the edge, and make sure you have lawn on one side and no lawn on the other. The choice of using an edg laterial or not is up to you, but by mowing the lawn and keeping a neat edge you will delineate the edge of the formal part of the garden (lawn) from the informal (woods). This will go a long way toward making the whole thing appear planned and cared for, which is what you are trying to do.

Thank you all for your suggestions. A spaded edge certainly fits my budget!

I have about an acre wooded lot also. I stopped mowing a strip about 20' to 40' wide between my lawn and the woods. I let the grass get long and let the violets, trefoil and boneset that comes up there naturally, grow. I do walk the strip occaisionally and remove or cut off individual noxious weeds like dandilions, thistles, ragweed and garlic mustard that will pop up in the unmowed strip.

I use the mower to define an edge in the tall grass by walking a gentle concave arc so it definitely looks like a controlled edge.

I plan to start adding woodland edge plants in this area, but am waiting a few growing seasons to see what will naturalize before I add anything.

Making an edge with a spade works. For some isolated beds I made shallow, narrow trenches with a spade and laid logs flat in the trenches. The trenches keeps the logs from rolling away and the logs make a pronounced but "rustic" border. The logs don't care if they are occasionally nicked by a string trimmer.

I did just the opposite! I trimmed low branches at the edge of the woods, pulled out the raspberries and shrubby undergrowth and planted phlox divaricata under the tree canopy. I also planted new trees in the lawn. The idea was to make the line between the grass and woods less distinct, more gradual. But then, my garden was literally an open space chopped out of the surrounding woods and neighborhood was pretty rural in character.

We have three acres. I cleaned out 15 feet deep into the woods around our lawn. I planted shade/woodland plants. It looked fine. Recently I acquired some rocks and managed to edge the entire lawn. It looks fabulous.