D'ohh... I should have been able to figure that out. It depends on your work-flow. I do 95% of my work in LR, including WB, colour & exposure correction, minor spot & dust removal, leveling & cropping (I sometimes leave this for PS), etc, etc. Generally in PS I'm doing things like cloning, skin smoothing, repairing backgrounds, compositing, etc. The actual "editing" as opposed to minor correction and enhancement.
Anyway... I get all the correction stuff done in LR and then export that as a .tiff/.psd, so that I have basically a two-stage process, and since the first stage is non-destructive, quality-loss isn't an issue. Time loss? Well.. yeah, sometimes.