i3 has really been amazing for me. It came to my rescue when I was looking to move to a saner desktop on Ubuntu and I am now hooked on the focus-follows-mouse model. I feel lost when I go back.
I'm working on an old intel core duo laptop with 2GB of RAM and thanks to i3, I have better performance than the i7 , 16GB for most tasks.
Some people might not need as much functionality out of the box as i3 offers, if you're one of them you should try DWM :)