Hi,
@PolishedGeek:
The main reason was that it wasn't working properly.
It was only redirecting you to the checkout.
And that's incorrect as it needs to first change the current cart to the cart you're looking at. Otherwise, you might end up with a cart different from the one you're looking at.
We were eager to release the 3.x series rapidely and decided it was better to remove it than having a broken button there.
But I agree that it's a good idea to have such button. It should however be named properly like "set as current and checkout" or just "checkout" when you aren't in mutliple cart mode, and it should display in the toolbar and not at the bottom to keep the layout clean. We'll look at doing something about that in a future version. Thanks for your input.
@sauvain:
I don't see how that's possible. Could you provide a screenshot of the whole page so that we can see what you have there ?