When I import a PSD file that has multiple layers into Lightroom what is the type/specs of the file you are editing in Lightroom. As Lightroom does not know anything about the layers in Photoshop there must be a TIFF file or some other file type that Lightroom is using. It probably isn't some JPG full size preview, at least I hope not. Is the color profile and bit depth the ones you were using in Photoshop? This is just for my general interest as it seems to work ok but I thought I would ask the EXPERTS.
LR can only edit PSD files that have been saved with the Maximize Compatibility option. This option stores a special compatibility layer in the PSD that is the merger of all the layers, equivalent to the result of Layer > Flatten Image. The compatibility layer has the same resolution, bit depth, and profile as the other layers, and of course it doesn't have any lossy compression applied.
Thanks for the info John. I have always wondered what I was editing in Lr when using a PSD. You explained it very well!