This is a work in progress. I needed to reenable gradient buttons in Bootstrap 3 for a project.

grad-buttons.less

// Gradient Buttons
// -------------------------
// Re-enable gradients for Bootstrap 3 buttons
.grad-button(@color, @grad-start, @grad-end, @text-shadow: none) {
	
	color: @color;
	#gradient > .vertical(@grad-start, @grad-end, 0%, 100%);
	text-shadow: @text-shadow;
	.box-shadow(inset 0 1px 0 rgba(255, 255, 255, .1));
	
	&:hover,
	&:focus,
	&:active,
	&.active {
		#gradient > .vertical(darken(@grad-start, 0), darken(@grad-end, 10%), 0%, 100%);
		color: @color;
	}
	
	&.disabled,
	&[disabled],
	fieldset[disabled] & {
		&,
		&:hover,
		&:focus,
		&:active,
		&.active {
			background-color: @grad-start;
		}
	}
}


/* Example usage (uses Bootstrap's Less variables):

.btn-default {
	.grad-button(@btn-default-color, @grad-start, @grad-end);
}
.btn-primary {
	.pretty-buttons(@btn-primary-color, @grad-start, @grad-end);
}
.btn-success {
	.pretty-buttons(@btn-success-color, @grad-start, @grad-end);
}
.btn-info {
	.pretty-buttons(@btn-info-color, @grad-start, @grad-end);
}
.btn-warning {
	.pretty-buttons(@btn-warning-color, @grad-start, @grad-end);
}
.btn-danger {
	.pretty-buttons(@btn-danger-color, @grad-start, @grad-end);
}
.btn-inverse {
	.pretty-buttons(white, #474949);
}

*/