I finally broke down and got the edger attachment this year. Big difference maker. If you have kept up on it you might be able to get by with the string trimmer but the edger is definitely a step up especially if you are trying to undo the lack of it being done.Another great question is - do you have a dedicated edger or use your string trimmer to do the edging?
I do both - if I'm in a rush I'll do it with my string trimmer, but 80% of the time I use the dedicated edger and get those nice crispy lines.