I have an early 2012 (non retina) MBP with 2.2GHZ i7 processor, 16GB RAM and 1TB SSD and am finding preview VERY slow when browsing RAW picture files. My MBP came with Mountain Lion installed, and when Mavericks came out I installed that but had the same issue with RAW files as I have now, so went back to mountain lion. I installed yosemite last week as Mountain Lion doesn't yet support RAW for my new Nikon D750 and initially preview worked fine. However, since yesterday it has started behaving how it did with Mavericks. What I normally do with my RAW files is open them all in preview (select all then open) to look through them and decide which are keepers and which will go in the trash before importing into lightroom. However, when I do this now it takes an age (3-5s) to go from one pic to the next. Whilst 3-5s might not sound a lot, when you are sifting through hundreds of photos it quickly becomes very time consuming. I am seriously considering going back to mountain lion and waiting for a RAW update. However, I don't know if they will as it requires the latest iphoto update which is only available for Yosemite AFAIK. Before I do anything drastic does anyone know of a fix for this, or possibly even another photo viewer that I can use to sort through RAW files? TIA P.S. Does anyone have the link to send 'feedback' to apple so that I can report this please?