Shotwell and Compiz's Screenshot plugin can help with his screenshot woes. But honestly, for the things you're evaluating Linux to be capable of... it's been quite capable for a while. Now with new software focusing on usability, I suggest that there are now enough nice pieces of software to create a very usable experience for someone who finds a Mac interface easy to pickup, my current setup is a no brainer for them. It has a familiar dock that looks sharper than apple's own dock and not tacky and hacked up. Cardapio has given me a main menu that is more capable and sanely organized than the Start Menu without being a folder full of shortcuts.

tl;dr Linux has /been/ capable. Ubuntu and other OSS community software has made it usably capable.