1) The media browser insists on staying in the foreground which is a bit annoying when going back and forth.
2) It would be great to be able to browse more than one folder level at a time -- Picasa's continuous browsing view through folders is a great model and much more usable when scrolling through many folders with multiple levels of hierarchy.
3) I was hoping that Affinity Photo would be "dual use" (for simple edits and more sophisticated work) since we have people in both camps at home. It would be extremely useful to have some basic "simple edits" in a mode more closely attached to the browser. Again, something like a Picasa set of simple edits. If the browser/editor were more coupled that might be something that could be done with a "basic edits" persona.
With Picasa losing support, I (along with numerous others I know) are actively looking for a replacement that has strong "browse" support along with basic edit. The Affinity platform is great on the edit side and will likely replace Photoshop for my use but having a "simple, browse centric" mode would vastly widen the appeal to more casual users (such as my spouse).