I found this old thread this evening while doing some more searching for oyster sauce as I was cleaning out the fridge and realized that the sauce within needed replacement. Since I started this thread 10 years ago, I felt I should bookend it.
Megachef is pretty darned good, and has become one of my go-to sauces.
Koon Chun, which I found at the local Ranch 99 Asian market, is also quite good, and I will be looking for another bottle of that briny elixir on this coming week's trip to the market. It's definitely better, to my taste, than LKK.
I'll take a look at Dragonfly when next I visit Berkeley Bowl, but my inclination is to avoid it as just this evening I watched a test and review of oyster sauces on Pailin's Hot Thai Kitchen and she was very disappointed with the product. Maekrua didn't fare well, either. Over the past ear or so, I've found that I tend to agree with her taste assessments more than not.