A nice overview of the new features and changes in Aperture 2.0 by the Aperture Users Professional Network, which seems to bear out some of my own first impressions. Particularly interesting might be the plug-in API, especially if it will attract some of the PS Plug-In writers, thus obviating the need for a round-trip to PS in many circumstances.
FWIW, here are some examples showing High-ISO shadow performance on a picture taken with a D70s at 1600 ISO, converted with standard settings through Aperture 2.0, Lightroom 1.3 and Capture NX 1.3, in this order:
The 100% crops show a nicely even and fine-grained noise background in the sky in the Aperture 2.0 conversions not matched by the LR or NX conversions (at least with standard settings). While not really visible in the crop above, low-contrast detail seems not to suffer as a side-effect of whatever Aperture is doing here, so this definitely seems a win for High-ISO work, like this hand-held shot at nightfall.
The crops above were all taken from the drainage pipe in the upper right of this overall picture of the Ammersee (to the west of Munich) at Nightfall:
Taken with a Nikon D70s, Sigma 10-20mm f4-5.6 zoom at 10mm, f4 and 1/25s, ISO 1600, hand-held.