I share the concerns of others about the massive size of .afphoto files. Using Photoshop, I can open a CR2 (Canon RAW) file and make whatever adjustments I need before exporting to JPG. However, a XMP file is also saved which contains a record of all the changes and adjustments made to the CR2 without the massive file size. So I can come back later, open the CR2 and so long as the XMP is there, it will open as it was last left. This is efficient.
The massive size of the .afphoto files is a big concern. I am a new convert to AP and I admit that I really like it except for this particular feature which has come as a rather unpleasant surprise. It will make archiving very expensive in terms of space and money. If AP had an XMP-type file format, I reckon that would solve most people's problems. Sure, the .afphoto is great during work, but for archiving, something smaller is required IMHO.