The "Small device grid" will be the biggest feature for me as bootstrap 2.x gave me some headaches implementing a simple 2 column grid on low resolutions.
Comments like my own are probably the reason @mdo would not like the docs made available to everybody as it spreads potential mis-information and sets expectations that every feature will be in the final product.
Fairly disheartening to watch the countdown hit 0 - Hit the register button immediately and spend the next hour being thrown back to the start for the progress 7 / 8 times to eventually find they are sold out.
I personally didn't get to see the payment screen but I hear many peoples purchases timing out or making purchases to have them cancelled after they sell out.
Comments like my own are probably the reason @mdo would not like the docs made available to everybody as it spreads potential mis-information and sets expectations that every feature will be in the final product.