So, I've bought my 2nd, 3rd, and 4th commercial mead yesterday, with a total of 3 meaderies tried so far.
1st: Smelled terrible - Pungent mercapto's and H2S, after airing out for OVER AN HOUR, it tasted alright, I would have bought it again, if I knew it didn't smell terrible/taste terrible on opening
2nd: Cyser, tastes like angry orchard with mercaptans in it, has an almost cracker & sausage flavor? Not drinkable past 1 glass.
3rd: Blueberry (definitely added in primary) melomel, blueberry taste has become some kind of sweetness, but tastes nothing of blueberries, or any berry. Strange.
4th: A semi-dry traditional, tastes like a low-quality white wine. Wouldn't buy again.
So far, my idea of what is "right" in mead is pretty chaotic. I've brewed better stuff than anything I've had commercially, but my stuff I can tell could still be much better.
One of the things I wonder about these commercial breweries is if they are adjusting pH and using nutrient additions. I would think so, but some of these mercaptan smells are making me second guess this - or it could be something so silly as temperature control.
Long story short - You'll know when you get it right by finishing one glass and wanting another.