Well, I might not notice a little bit of out of alignment but I could on one frame that something wasn't right, that it took seemingly a log of energy to make it go.

When I first rode my Gran Sport, a bare and slightly abuse frame I got really cheap, I discovered it had been stretched to 126. I also discovered that the skewer didn't always grip the DOs enough. It turns out that the DOs weren't aligned very well, probably from the stretching process. Once they were straightened the axle slipping stopped. If you're going to stretch the rear, do check that the DOs are parallel to each other and the bike's centerline.