Mark, My suggestion is that you first make all of your managed photos referenced ones in one single folder. Once there it is best that you go through your pictures, ratings, albums and smart albums, etc. Flagged rated photos will not carry over but starred ones will.  Any books that you created, will not carry over as a completed book, but the photos in it will.  You can use the transfer program in Lr to move them, or use an app program (I think it still may be around $12-14) called Aperture exporter.  You can purchase it from the Apple App store or from the site itself.  It has several walk through tutorials on the process.  I found these youtube tutorials by Todd Olthoff & Thomas Fitzgerald to be extremely useful.  Here are the links:

Moving from Aperture to Lr-Part 1

Moving-Part 2

The difference between Aperture & Lr

Using Lr’s Mover

Hope this helps.  Having done this at the beginning of this year I was a little hesitant but I found it is not as daunting as you think.  The key is  getting all of your images into one folder and having them referenced.  Of course, having a large enough storage location is also key.  I use an external HD.

Cheers,

Florian

I finally did mine this weekend.  I used the Lightroom Importer for it and it worked like a charm but took an entire day.  I had over 30,000 photos.  I followed the info here and it worked just like it said.

 http://landing.adobe.com/en/na/products/creative-cloud/54511-aperture-sw…

Before moving my photos I have spent the last couple of months playing around in LR so I understood how it worked and kept using Aperture as my main program.  

I bought LR a year ago.  My new pictures have been going in LR and I’ve kept my old ones separate in Aperture. After a year I am becoming very comfortable with Lightroom and think I am ready to make the move.  I bought Aperture Exporter but decided not to use it.  I determined that Keywords and metadata are the most critical part of the move, NOT the edits. I have chosen to move my Aperture photos 1 Project at a time.  I am just moving my originals + meta data over in most cases and losing my edits.  I’m a much better photo editor now than I was 3 - 7 years ago and so I’m not really losing much good work, however some photos have hours of edits (a few family restorations) in those cases I’m moving the Original & creating a “burned in” Copy.  I have about 40,000 pics, but no hurry I suspect it will take 5 or 6 weekends and I’ll finally be moved.  Still cussing  I loved Aperture, I find LR, ugly, and unintuitive - however I have come to appreciate some of its tools and its integration with Photoshop.

Mary I too am gaining a lot of “organization” by moving from my “managed” Aperture library to my “referenced” LR Catalog.  Been changing a lot of file names and folder names and moving files into the folders they “should” have been in all along.  I have always been lazy as my key  wording is very strong so I always felt I could find any file I wanted.  Its slow boring work but I do like how much more organized I am in my referenced system.  Wish I had done that in Aperture all along.  Its also fun seeing a bunch of my old photos…some good stuff there. Still very surprised how bad some of the LR tools are vs Apples (talking to you Adjustment brush) and how bad some of Apples were compared to LR (talking to you shadows and highlights slider).  

One question - is Aperture as slow as LR is when you have it referenced vs managed?  I only had Aperture Managed and it has always been wicked fast.  LR is a slow poke. I’m going to buy a new iMac and faster HDs to try and speed LR up but its really “laggy” for me right now especially as I move files over and the catalog is growing by thousands of pics a week.