I've only sent a couple rolls of Kodachrome to Dwayne's in the past year or so and they came back just fine with no problems. They even called me with a question on one order and the lady was helpful and friendly on the phone.
That being said, I sent them some 120 B&W for processing and scanning that I didn't want to do myself for some reason and the scans indicted there was a lot of dust - more like fuzz or hairs on the negatives that weren't blown off before scanning, so I think they have room for improvement on their cleanliness.
I still have one roll of K200 and one roll of K64 in my freezer that I suppose will get shot and sent to them before the end of next year, but it seems to me Kodachrome has been suffering a long and slow death. I wish it was like the old days when I could drop a roll of Kodachrome off at my local K-Mart and it would get sent to a Kodak lab in Chicago or Dallas and would come back beautifully processed with lovingly care.
I'm ready to move on now and have been exploring Kodak's line of E-6 films which I can get processed locally. I'm really impressed with some of these as well as some of Fuji's transparency films. Yes, I'll miss Kodachrome since I used it for so many years, but it looks like I'll get along just fine without it. Like others, I prefer more selection instead of less.