The Adobe importer doesn't even attempt to deal with photo adjustments made in Aperture. There is really nothing that translates image adjustments from DAM to DAM. You have to export the adjusted images as TIFFs or JPGs or whatever. Many of us leave some of those in Aperture if you need the non-destructive edits. If they are RAWs, of course, they aren't ever changed. The exporter in the Mac App Store (or on their website; you can download a demo) has some bulk exporting features for images that are edited.
Metadata is relatively easy. Of course one option, even without an importer, is to write that to exif and/or XMP sidecars, and that's prudent as a backup strategy no matter what you use. I don't see any reason to NOT do that; sometimes in day to day use people turn that off to speed things up but I like the redundancy. YMMV. And then the metadata is truly independent of whatever software you use, even Spotlight and non photo applications. This seems to be overlooked by many Aperture users since it's a tad less automatic than with LR, although both applications can do it. Not so with iPhoto.
Keywords, geolocation, etc. all come over. Faces are written to keywords, but not the face space (i.e. which face is which). Labels and stacks are also written to keywords. Projects and other virtual containers map over to collections and collection sets in LR, but there are some differences. Your referenced files can stay put.
Specifically, projects produce slightly different results, because a project can contain BOTH individual photos AND containers. In LR, a collection set can ONLY contain containers, so LR makes a project into a collection SET and a collection within that set that contains the individual photos that may have been in the project. Essentially it just moves them one level down.
I've posted more details in a thread over at dpreview.com in the Mac forum.
