I see no point in cataloguing an image that will probably be deleted later.
All of my files get renamed, captioned, keyworded, etc., before the first round of editing. This happens in Photo Mechanic, then the photos are imported to Lightroom for processing and, at home, cataloguing. I find it much easier to do this right at the beginning, after downloading the photos from the card. If I wait any time at all, then it never happens and I end up with many gigabytes of photos with no metadata that I might as well not have shot.
This has not always been true, of course. I've been doing it this way at work since I made the switch to digital in late 2000, but at home my personal photos were a mess. I had hundreds of GB of photos with inconsistent filenames, terrible organization, no keywords, etc. The only thing I sort of had going for me was a reasonably careful folder structure, year>month>shoot. So, I installed Lightroom and pointed it at the folder of personal photos, and let it Import all of them in their current location.
I have spent the last couple of years going through that archive of personal photos, carefully keywording, rating, and deleting images. I'm not done yet, of course, but it helps pass the time at home
I find Lightroom immensely helpful for this process - there is no way I could do this as easily and consistently with other apps, or just browsing through the hard drive in the Finder.
After spending some time working on my backlog, and -- more importantly -- keeping up with metadata on my new photos, I find the organizational power of Lightroom is pretty cool. I have set up numerous Smart Collections, virtual folders of images that meet certain criteria (keyword contains "portfolio" and rating = 5 stars, for example, or keyword contains "daughter's name" and rating = 5 stars.) These make finding photos a breeze, or, anyway, more of a breeze than before.
If your 100GB of images is in some sort of rational folder structure, you could do the same thing: Import all of them into Lightroom (keeping them in their current location), then use the organizational and editing tools in LR to keyword, rate, edit, and then develop your final images. I'm also very happy with the Print module, which is much easier to use than printing directly from Photoshop.