The biggest knock against LBS mechanics should not be how skilled they are - you clearly have some compentant people to pick from. The knock should be the kind of work they often do. Many of us have stopped using LBSs for repairs simply because of the work that gets done. You drive across town to take it in, you wait a week and if it's fixed at all, something else is often wrong.
I have little doubt that there are 1000s of LBS wrenches that are far more skilled than I am. But I'm pretty sure that there are very few that have the time or are willing to invest the time to do repairs on my bike the way I do them. I honestly doubt that many wrenches with a typical workload can afford to spend an hour tweaking my RD and taking it out for test rides. That's the kind of dedication I give my bikes because I like them to work perfectly. I honestly can't expect anyone in a retail situation to do the same and in my experience that has often been the case. For me it's faster and less frustrating to just do it myself.
I think the LBS service industry does a great job for people that often don't really know how well their bikes can work. The problems lie with with mismatched expectations. Experienced, perfectionist customers and busy, harried mechanics. And yes, there are extremes on both sides - nutcase customers and lame wrenches. I just don't think the extremes are indicative of the real world.
And oh yea, I'm an engineer too.