I would suggest reading the SpecMiata.com boards on this subject.
To summarize: Many people are seeing higher wear rates, and the treadwear number changed, but Toyo is telling us that there has been no change.
Some have said they seem a bit quicker. But there's really no hard evidence of either higher wear rates or faster times. It's just a feeling some have had.
Toyo is trying to get to the bottom of it. We'll see I guess.