Just as soon as I make the switch and proclaim my allegiance, Apple releases Aperture 2.0. After downloading (and messing around with) a trial version, I've decided to stay with Lightroom. BUT... I have found a reason to use Aperture 2... tethered shooting. A2 makes tethered shooting a breeze... and A2 also allows the use of a fullscreen second monitor (which clients seem to dig). So after all the deciding, looks like I'm going to be using Aperture 2 for shooting, and Lightroom for processing.