Did you export your raw files you edited in Aperture to jpegs or did you start from scratch in LR? I have thousands. Luckily the Aperture meta data appears to be fine in LR
Here are a few ideas to consider:
Is there no finer DAM than Aperture? - Look behind the UI and I think you will find nothing can match it in terms of capabilities. Yes, speed is not up to par as compared to say Photo Mechanic, but for purposes of DAM I have found nothing finer.
I tried LR (v4) on a few thousand images, DAM just doesn't come close. RAW processing is good, but even using v. 8.3 it simply cannot handle high ISO and highlights as well as others. The rest of its rather fine set of post processing tools are steps ahead of Apple at this time, so that left me thinking to use the best parts of what Aperture offers, and via its flexible plug-ins use others as necessary.
For me, what it came down to was raw. Aperture gives you lots of choices about how much post processing you let it do. I do not give Aperture any permissions to do anything but be the DAM, particularly since I find its raw engine severely lacking
I do batch raw editing as well as JPEG editing in DxO Optics Pro using Catapult as my export and re-import mechanism. (there are many other good raw processing apps that will work with Aperture, so while I depend on DxO, it does come down to individual choice).
In most cases to bring my images up to my levels of quality is accomplished using raw processing . If more processing is desired I have choices to work off the reprocessed raw (usually a 16-bit TIFF) out of Aperture then into NIK's suite, DxO Film Pak, and PS6 and then back into Aperture.
So, my workflow baseline is Aperture and via plug-ins everything else just seems to work pretty well and my round tripping is simple. Aperture's stacking capabilities are remarkable in keeping my workflow consistent yet flexible, allowing my versions to be in one place, tracked using great metadata capabilities.
These are just a few ideas about why when you look at an app as complex as Aperture is (i.e. the user manual is over 500 pages today), it really can't be as simple as some argue.
Just my $0.02 worth of thinking....