Yeah I went from 2014 to 2017, and went from broadly not worrying about doing 6 hours of solid dev work without thinking about battery to essentially never feeling comfortable away from a plug.

I'd guesstimate I get at most 3 hours on the 2017 before the battery level gets low enough I have to start planning where I'll next plug in. Not ideal.

part of the issue is if you have anything other than textedit open, the discrete GPU is on hoovering up all your watt-hours.

It is, but I haven't found it to be significantly worse. About an hour less.

Many people would describe an hour's difference to be a "significant" change, especially when a scale of around 10 hours total battery life is being considered.

Sure, but considering the "fudge factor" that Apple often applies for their battery life estimates ("casual browsing", etc.) an hour isn't all that much.

I think decaying batteries might drive people to get new machines? Just a suspicion. They do it with iphones :p

It’s certainly an incentive to upgrade, but only if the newer model is a clear upgrade...

I suspect that Apple will be seeing a lot of 2015 MBPs brought in for battery replacements...

All batteries decay.

I concur.