This is a bug in 2.0rc2 introduced by the restyling of the grid headers. We never have centered headers in the product, so we styled them for the default left alignment and accidentally broke the center alignment.
You can fix this in your app by adding the following css override in your app css:
.yes-harmonized .rally-grid.x-grid .x-grid-header-ct .x-box-inner .x-column-header .x-column-header-inner {
display: block;
}