When users say "lightroom has slowed down" with D800 files, they really should to be more clear about what is slowing down...
- preview generation (zooming in to 100%) in Library or Develop?
- lag time with making value adjustments?
- lag time with spot removal, graduated masks or adjustment brushes?
- generating output (e.g. Export to jpeg) or
- all of the above.
I am running LR4.1 on a MacBook Pro (mid-2011) 2 GH Intel Core i7 with 8GB of ram. I have noticed a few "slow down" issues with zooming to 100%, spot removal and Export. Upon import I do not have 100% previews automatically generated for ever image. So, when zooming in, I must wait for the Preview to be generated - that takes a second or two. Spot removal takes a second or two, but is not (at this point anyway) annoying. Exporting to jpeg takes notably longer.
Note: Mike Guilbault mentions about closing down other apps while working with D800 files - an excellent idea! Also, I found the article on Optimizing Lightroom
on Adobe.com very helpful: http://helpx.adobe.com/lightroom/kb/optimize-performance-lightroom.html
In particular, setting the Camera Raw Cache settings to 20GB or more.
I've gone from 12.5MP raw images to 40 to 50MP raw images, yet the speed hit is not really an issue. But, then again, perhaps I am just trying to convince myself that I really don't need to spend another $2000 after having just spent $3300 on a D800e.