It would also be noce if Aperture allowed the user to make some use of the embedded preview in the DNG file.
Yup - Aperture's DNG is definitely a bit awkward at the moment. Given Apple's philosophy about not touching masters for any reason at all, I guess I'm not confident of them eventually doing a DNG update with a freshly rendered preview. It's going to be hard enough to see 'em rewrite metadata in a DNG header.
That said, I find Aperture much less clunky to use as a general image navigator than Lightroom at the moment. Whilst I could really use the (promised) tighter integration between ACR and Lightroom conversions (and it looks like they're nudging the ACR4 basic parameters towards Lightroom), I'm just not that excited about the Lightroom interface. I guess I'll need to check it out again at the 1.X release...