To test the new, awful glossy iMac screens I had to dabble with Aperture.
Maybe I just didn't get access to all of the editing tools, but Aperture seemed pretty basic to me, in comparison with LR 1.1.
I could not find any curves, just the contrast slider. And no vibrance, just the saturation slider.
Those two things alone make me feel good to have chosen LR over Aperture.
But I found one thing I liked more: you had full access to Metadata even when editing. In LR, you have to switch back and forth between Develop Modul and Library Module.