To be quite honest, the hardware in the rMBP isnt enough to deliver a consistently smooth experience across all applications. At 2880 x 1800 most interactions are smooth but things like zooming windows or scrolling on certain web pages is clearly sub-30fps. At the higher scaled resolutions, since the GPU has to render as much as 9.2MP, even UI performance can be sluggish. Theres simply nothing that can be done at this point - Apple is pushing the limits of the hardware we have available today, far beyond what any other OEM has done.
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Some elements of drawing in Safari for example arent handled by the GPU. Quickly scrolling up and down on the AnandTech home page will peg one of the four IVB cores in the rMBP at 100%
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Throw a more complex website at it and things get bad quickly. Facebook combines a lot of compressed images with text - every single image is decompressed on the CPU before being handed off to the GPU. Combine that with other elements that are processed on the CPU and you get a recipe for choppy scrolling.
While last years MBP delivered anywhere from 46 - 60 fps during this test [facebook scrolling], the rMBP hovered around 20 fps (18 - 24 fps was the typical range).
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Whereas I would consider the rMBP experience under Lion to be borderline unacceptable, everything is significantly better under Mountain Lion. Dont expect buttery smoothness across the board, youre still asking a lot of the CPU and GPU, but its a lot better.
With the Retina MacBook Pro I get the distinct impression it was launched before the software was ready to support it.