Human bones will break at 45 G's or something.
If someone was going into 2 G's, it would be a hell, everything was heavier, not only you, but also the keyboard, your bag, lol, everything, I doubt people would like that, some could even die because their heart would be have to endure too much presure from the weight.
Our body is build for this kind of gravity, if it would be twice as big, you'd have a big problem.
I once saw something on Discovery Channel, that people born on a planet where the gravity is twice as big as here, that they also will be allot shorter, muscular too, heavy build, but also allot shorter, gravity doesn't allow long heights.
You'd have muscular hobbits then.
And if gravity would be half of what earth has, they would become longer, over time ofcourse, and wouldn't need as much muscle as those body-builder hobbits.
Needles to say, those guys wouldn't be able to survive on earth, while the hobbits would go mad here coz they would be overly strong.
Gotta love Discovery channel.