Please make the open dialog that appears at app launch optional. It's quite un-mac-like to force this dialog on the user.
And please, never open a file dialog when an image file is dropped onto Pixelmator or when Pixelmator is re-activated via command-tab or any other means. The file dialog appears below the opened window and is completely useless.
Just one tick-box in the Preferences, please...
What features would you like to see in Pixelmator Pro?