I don't have a MBR yet, so I can't comment authoritatively on this topic.
However, I strongly suggest you sample the new machine with the new system update to see if it meets your expectations. Slow scrolling can be easily fixed with system versions - and that explains why the issue has disappeared. But the first generation of a new product will nearly always have glitches that will be addressed by future versions; they're underpowered to make make for a stronger v2. (That's the strategy for the iPad Mini.)
If you can wait, settle for the 2013 release.
Thanks for the reply.
The issue mainly narrowed to some sort of software problem in the scalling algorithme on multiple discussion. But most were still questionning if if could be resolved or not by software optimisation.Usualy Apple get product out with "balanced" hardware.
So im simply looking for some answer of satisfied people on the smoothness of the Macbook Pro Retina in overall.