Resurrecting this thread, as I have a stay at Hyatt Regency Amsterdam, and there is a new rate that is 50 euros per night cheaper than what I have if I book as one person. 25 euros less if I book as two people.

I would definitely be registering my wife (so she can get new keys whenever needed).

Seems like opinion is split on the practice of booking for one and changing it at the desk?