As everybody has stated before, it depends on the property. When you book a room you will see the different prices for different rooms, especially when you travel to vacation spots - city views vs scenic views, regular floors vs executive floors, etc. So if you book the less expensinve room - city view - and when you check in you get the scenic view, then that is an upgrade.

Tuesday I checked in a Garden Inn and I was told at the front desk that I was upgraded to a suite. It is a nice hotel and very new, less than 7 months, and the suite was the size of three regular rooms with a king bed and double baths.