Cornies are great for mead, and wine too for that matter. The only caveats, as I see them, are two: one, you wouldn't get the same gradual oxidation over time as one would through a wooden barrel (or, to a lesser extent, through a natural cork). That's a good thing for whites; you can omit the buckets of sulfites that wineries use to offset O2. This might mean that if you wanted that oxidative character in say a bigger red that you're "laying down" for a while, you could rack it every six months or so to expose to air. Two, unpressurized cornies can "sip" air in around the racetrack gasket. For example, if the keg cools and atmospheric pressure gets high, there may be enough negative comparative pressure inside so have a burp of air intrude into the keg. Some will recommend putting 5 psi of CO2 onto the wine/mead, but it will soon dissolve into solution leaving little head pressure.
In practice I haven't found this to be a problem. If it worries you, William's Brewing sells a larger, softer O-ring that should seal you more tightly (it's intended for leaker kegs that don't seal accurately).
No flavor contribution. Most commercial wineries use stainless. There are even computer-controlled "micro-oxygenation" systems to allow the wine to age more traditionally.
Note that mead in kegs will not be able to offgas, so make sure it's done unless you want a sparkling mead. Though it's easy enough to offgass a keg as you know! I tend to put in cornies after a couple/few months in glass.
Dispensing could be done by nitrogen so as to not carbonate the mead. One can even rack by CO2 pressure to a new, purged corny, preventing any air contact at all. Cornies rock!
The militant steel vs. wood argument, to my mind, illustrates the differences between winers and winemakers, if you catch my meaning, though there certainly are legitimate differences. Use the cornies.
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