Recently upgraded to PM 6 and so far I'm regretting it. I still have 5 on my laptop and refuse to upgrade my laptop right now because of the issue I'm seeing with PM6. When in 5 using the arrow keys and I was color tagging images it was very fast. But now on version six it reminds me of why I left LR for for sorting and tagging. Its like pulling teeth very slow unresponsive and laggy. I have changed the preview image defaults and it has improved a little bit. Working on a brand new iMac eight core 64M Ram, I would expect things to fly. Both PM5 and PM6 I would work from a Promise NAS running over a Thunderbolt connection. Some of the articles I have found on here talk about how PM6 works best used locally. If that is the case did something change from PM5 to PM6. PM5 seemed to be able to manage very well on my 8yr old iMac from a Promise NAS. Trying to find a solution before I scrap 6 and just go back to using 5 on all my machines.