Just curious having never flow partner flights with other alliances, is ST the only cluster or are do the others have their quirks too?
In my own experience, ST is more a loose and warring confederation than an integrated alliance. I'm sure that DL is very careful to reap the revenue that it is due, but no obvious investments have been made to improve the customer experience since the NW/KL merger. SkyPriority across the "alliance" means less to me than having seating assignments stick and dealing with clueless agents.
Star Alliance, while not perfect, is not the dysfunctional kludge that DL/AF/KL is.