Same here. I tried to upgrade a UA flight, called the SEN line and they told me how it works (since the upgrades on the star website seem never to work):

First they have to amend a copy of the UA reservation on Amadeus (so different Res. No). Then they send this as a request to United. United repsonds typically within 48 hours.
If the upgrade is confirmed they will send you a paper version of the eVoucher or an upgrade coupon (and take the miles from your account).
They normally send it only to your registered address, not to a hotel.

Sounds really high tech.....