33% greater productivity
Not quite sure how you measure that... I'm sure the one less keypress is outweighed by all the "WTF?!" moments when you've accidental typed only 1 instead of 2, compiled the code and it's done something weird! 
So far my "WTF?" moments have been restricted to forgetting an if comparison is double equal sign, not a single! That really does throw the program logic... It appears an assignment always returns true! :-[