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15-20% performance boost in the CPUs Apple will use
Graphics performance could see something like a 60% boost
Better battery performance but unlikely to be very significant

Are these real world, imaginary, or technical stats?

As in "30% increase in battery life!" = maybe an hour, max, if lucky.
 
"The new Core M Skylake processors offer 10 hours of battery life and 10 to 20 percent faster CPU performance compared to the Core M Broadwell processors used in the first-generation Retina MacBook, along with 40 percent faster graphics performance."

From the article. Deeddawg is spot on, if you aren't hammering it or don't notice any wanting for extra speed at the moment the difference will likely be minimal. However, if 10 hours of battery holds true, that may make a big difference given the value of portability and how it's basically tied into the design of this mac.
 
However, if 10 hours of battery holds true, that may make a big difference given the value of portability and how it's basically tied into the design of this mac.

It depends on whether or not they're using the same metrics as Apple does in their "Up to 9 hours wireless web / Up to 10 hours iTunes movie playback" claim for the 2015 Macbook model. Does the Skylake claim mean 11% more battery, or does it mean something more noticeable? I don't know.

... and once again, if a person isn't already running into the limits of the existing model's battery, having additional battery life may not make much difference. If instead you're already frustrated with battery life and a little bit more will make a real impact, then the update would be worthwhile. All depends on the particular person's usage/needs.
 
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