To say the app fully supports editing spreadsheets online gives way to much credit to the developers, who have chosen simply to link the "edit" button in the app to the URL of the document on Google. Technically Safari for iPad supports editing just as fully and it doesnt cost $4.99. I even had to sign into Google because the app didnt use the profile it asked me to create for signing into my Google account.
Devvyn about GoDocs for Google Drive & Google Docs, v2.7.2