One note of caution: it really does take a week -- sometimes more -- for the system to sync your CO status to your newly-linked UA status. If it doesn't sync by the time you check in for the first segment, then US will just see you as a dirt-level CO member, and you won't get the usual *A elite perks (primarily early boarding + free checked bag). I don't know what happens in terms of RDM/EQM crediting if your CO status syncs to UA after your US flights but before the segments post.