had missed that thanks for sharing. I have been using custom dimension for uId in our client projects its worked out well, though a dedicated api method is always welcome.
Custom variables don't let you consolidate on users though? In the visitor count, for instance, I don't think there's a way to tell GA to use a custom var to distinguish between visitors.
yes there isnt a way within GA to aggregate metrics based on custom dims at the moment. we have on occasion done it through reporting api using cd to maintain a unique count.