Don't have to tune for it if the vehicle is flex fuel from the factory, it adjusts for the ethanol content regardless of concentration. Now those that use it for the track I can understand wanting to test to be sure what their tuning for. As for oem applications the only thing that's really important is the cost ratio-v-regular fuel if it's worth it to buy a tank or 2.
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adjusting for ethanol content and actually tuning to take full advantage of the ethanol are 2 very different things. Just like tuning gains on 93 octane, there's a lot left on the table with a factory e85 tune.

 

According to both 5* and MPT, I asked both of them as I have both companies custom tunes about tuning for E85 and they both told me to just run the 93 performance tune that I have from both of them and the computer will self adjust to accommodate the ethanol.

E85 tunes are specific for vehicles that are NOT oem equipped to deal with it.
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That's because on the 5.0 there's a table for Ethanol content ignition timing compensation based on ethanol percentage. So yeah of course it freakin works.

 

I run 60-70% blends on my 17 3.5 2nd gen ecoboost with downpipes, intercooler, drop in filter, exhaust and what not. No issues. Can definitely feel a difference.

 

I've run a few tanks of E85 through my '15 5.0 and it does seem a bit torquier throughout the rev range. I'm curious if the 15-17 5.0s still pick up ~ 15 hp and 10 lbf ft like the 11-14 trucks did, but I haven't been able to find a dyno test comparing E85 to regular with a stock tune on the same truck.

The truck adjusts to the higher ethanol content pretty quick... I can watch mpgs fall from ~17 around town to ~13.5 on the same routes. When regular (85 octane at this elevation) was $2.75 and I could get E85 for $1.99, a month ago, it was a pretty good deal, now that E85 is up to $2.24 you pretty much just break even.