Integrating the file chooser with Nautilus is awesome. I think it should have happened ages ago in the Gnome 2 era, when there were facilities for embedding a widget from one application in another (e.g. Bonobo). It is infuriating that there are small differences between the file chooser and the file browser. Windows gets this pretty much right, since it uses a special shell widget in the file picker. You get all the same context menus, and can copy files between windows via drag+drop.

The new image viewer looks nice!

Theming is a bit disappointing - instead of accent colors, I would prefer full support for themes, but that ship has sailed for Gnome.