Please tone down the rethoric andreas. I don't think that kind of language adds to the discourse. I understand you are frustrated but I have been nothing but helpful here. I see no reason to keep people from purchasing new hardware that is highly unlikely to run Lightroom slower than a several generations old C2D machine. Every experience that I have had with LR 4 on all kinds of different hardware tells me it should run far faster on that iMac. The reports in this thread and I have followed almost all of them from the beginning as I was considering a new machine myself have not changed my view on that as I saw it run on several modern machines owned by friends and work just fine. I tend to weigh personal experience a lot higher than reports on a web forum in deciding on a purchase. I also tried it on a retina machine at the Apple Store (they will let you do that if you ask) and it ran great there too. That said, I am convinced that the people that are reporting issues here are having real trouble so I don't want to downplay that. I am entrigued about your retina experience though. It is curious that the same hardware would work differently. Mine is just buttersmooth and I even store my images on an external USB3 hard disk (Catalog on the SSD). Not even a thunderbolt drive! Certainly a LOT faster than the C2D Mac Book Air I ran it on before that. Even when I had the images on the internal SSD on that one. I upgraded my machine to Mountain Lion when it came out and run fairly little stuff on it, just Lightroom, Aperture, Apple iWork apps (love keynote for slideshows), Microsoft Office (yeah retina aware!), XCode, Spyder Pro calibration software, and a set of browsers (Safari, Firefox and Chrome). LR 4.1, 4.2 RC, and 4.2 all work(ed) normally. LR 4 is a lot faster than Aperture for developing images on this machine. Aperture is somewhat faster at browsing images and the retina support on it is great though but I like the results from Lightroom a lot better.
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