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Strange. I've never experienced it. Which iGPU and which version of MacOS?

Maybe there's things running the background slowing it down.
Its happened on everyone I've tried, various combinations. Its the reason I've waited so long to make the jump to retina. Thankfully the 2016 13" is lag free :) Type "Retina UI lag" into google if you don't believe me. Some people don't notice the frame rate drops, so if you have not noticed it be thankful.
 
Benchmarks will show that hd 530 (15 model) will be weaker than hd 540 (base 13 model) and you'll have ui lag in your shiny 15 inch mac forcing you to buy the updated next year model which will solve all these first generation problems.
Thanks for the info. I've preordered both the 13"/15" mbps...but I'm leaning towards the 13". If I feel the 15" iGpu is not up for the job, that'll be the one to go back
 
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