John's right; projects were Aperture only things while a folder in Lr is essentially a folder in the Finder. I would like to see a notes feature too, both for images and for collections (I am leery about using them for folders within Lr however, since they wouldn't apply to the folders outside of Lr in the Finder).
And the comments field in Aperture was always kinda lame in that it wasn't readily visible and IIRC not searchable.
For individual images you can use the Instructions field in metadata. It's standard, visible outside Lr, and easy to use. But individual. You could add info to each image that's the same of course, and that has the virtue of being safe. Like "crop these so the telephone pole is eliminated and make sure the GPS metadata is deleted if they get published." But that doesn't suit as well for say a folder (better: collection) of disparate images, with like "pick the best one for BW treatment and edit out all but Bruce's face if it's in it, and be sure to include some with his wife, but make sure they're not in the same set with shots of his girlfriend."
For collections and folders I have done this workaround. After import I always have an image I'm gonna delete. So I rename "_index image" or something (that will sort first by filename; I might even change the capture date if I wanna get fancy but usually not). I often label it and/or change it to BW so it stands out. Then I use the IPTC instructions field and caption to add info like the kind you're describing. For me, being able to associate this collection with other non-image files was key, so sometimes I included a file url in the metadata too. Essentially this "image" is all about its metadata and not the picture (I kinda swiped the idea from a plugin that turned text into a jpeg you could read in Lr, only using metadata instead of the picture of text).
This also kinda fit into what I do to take notes in the field; I'd take a short video with audio and then import that into Lr along with the images, and that video would have info I'd use for the same purpose. I'd prefer a better solution (I now use Evernote, but it's got issues too). Saving PDF notes is great if you use Bridge.
BTW, I'm trying to get the developer of GhostNote to support notes IN Lr. It does in Ps: you can add a note to an open Ps document, and that note will then also be visible from that document in the Finder. Add your voice and demo GhostNote if you agree.
