I wish they could've increased the battery life.
This is one item that continually frustrates me with Apple. I know the effective battery life has varied greatly from iPad to iPad (with I think the OG iPad Air coming in around 13 hours), but that has slowly declined over the years. Granted my iPad Pro 10.5" is nearly 3 years old, but the battery life is pretty sub-par. In 10 years Apple hasn't raised the iPad's "All Day" battery life from it's standard 10 hours. And while I never get Apple's stated life, I get excited when they increase it even by an hour because I should see SOME kind of improvement.
I was really disappointed in 2018 when Apple made the redesigned iPad Pro's even thinner. I would think if there was ever a case for a slightly thicker and heavier iPad, make it the Pros and let the iPad, iPad Air, and iPad mini focus on that sweetspot of size and battery life. Apple could couple a slightly thicker design with energy savings form the more efficient A13X (or ramp up the performance that much more) and have 12+ hours. Even the 2013 MacBook Air had better battery life. Instead they seem to be happy with the 10 hours and use all optimizations to increase the thickness and weight of the device.
The iPhone 11 Pro is the first mobile Apple device where I'm truly happy with the battery life.
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I didn't upgrade to the iPad Pro 2020 primarily because of the A12Z. I know it's plenty fast now and will be fine for years to come, but I don't see Apple waiting another 18 months to update the iPad (making 3 years they used effectively the same chip). I think this update just tells me that there will be another update within the next year and I'm fine waiting especially since the A13 was such an important update for the iPhone, I'm excited to see the iPad implication of the A14X.