I have a 10+ GB Aperture library with thousands of pictures. When I now opened Photos for the first time I got asked whether I want to convert my Aperture library into a Photos library and agreed. However, only about 5 percent of my pictures are now in Photos - the library has not even 500 MB. Moreover, when I open now Aperture I have no pictures at all in there. This looks like a big - but bad - joke to me. Will be interesting what Apple has to say to this.