I would like to be able to customize colors, gradients, etc.
I would notice the following:
Perhaps one of them will help you, if not, create your own button library .
I use the fancy-buttons sass plugin: https://github.com/imathis/fancy-buttons Its fully customizable.
Sassy Buttons is another Compass extension for creating CSS3 buttons (with corresponding backups for older browsers). It is highly customizable and offers a variety of gradient, text and button styles from the box.