Just about all of my pictures have been digital since 2006.
I've moved from iPhoto to Aperture, from referenced (outside the iPhoto/Aperture Library) photos to managed (inside the iPhoto/Aperture Library. Now I'm migrating to Lightroom.
Moving to Lightroom also involves moving everything back to referenced photos.
Adobe helpfully made a migration tool to move photos from Aperture to Lightroom. That does a lot of what I want to do, but I need to move my pictures first. Sadly because I want to have all my photos in a folder structure of Year->Month->Event->Photo.CR2 I need to export things on a month by month basis.
So for every month I select all the photos within it, select Relocate Originals, and then let it run. Aperture isn't the fastest* at this, but it's speedy enough. The largest months (4000+ photos) only take about a half hour.
Nonetheless, at around 100 months (late 2005-2013) I have a lot of pictures to move. This method has the added bonus of being non-destructive to the existing Aperture Library in case Apple's new Photos app turns out awesome**.
Oh, and that's before I get them added to Lightroom. At least that's pretty automatic.
*Fastest being if it could move things as fast as dragging photos from one location to another on the same drive.
**It's probably not going to be that awesome for my purposes, but I can dream.