Maybe 5 years ago I thought I'd give the local chainsaw dealer a chance to sharpen a couple chains, mainly to get all the cutters back to an even length. I dropped the chains off before work thinking that they would have all day to sharpen them so they would take their time and not destroy the chain. Well, when I stopped by after work to get the chains, they weren't done. I said to the guy "no problem, I'll get them tomorrow." He said "no, just wait here and I'll do them." I was about to scream "NO" but I figured maybe he can do a decent job, plus they had a bunch of really nice mowers there that I wanted to check out.
When I saw the chains, I was flabbergasted. All the cutters were blue, like he hit them with a torch! The teeth looked like crap and were probably less even than my hand filing job. I just turned and walked out and have never been back since then.
I bought a Northern tool sharpener for $99 and have sharpened all my round ground chains with that ever since.