United comped me GM to Prem Exec (their gold-equiv) no problem.

I mailed a nice letter saying I would be flying to Chicago a lot along with my delta statement - received credentials pack within 2 weeks.

Address is:
United Airlines
PO Box 28870
Tucson, Arizona 85726

I haven't "defected" 100% from DL - our company has a 32% discount with them - but I no longer to the LGA-CVG-ORD silliness - just non-stops on UA now.

Takes a little while to get in the swing of things on other airlines upgrade plans - but it works out eventually.