Google Plus got a major makeover today and the biggest problem users are reporting about it is the excessive whitespace especially on a widescreen display.
The problem is intensified if you are on a 30” or larger monitors. Some users are even mocking the problem by showcasing the amount of whitespace on a multi-monitor setup!
In any case, Whitespace Remover for Google Plus is a browser extension for Google Chrome that might temporarily fix the problem for you. Get it here.