serpens

Hotel's official name: Doubletree by Hilton Amsterdam Centraal Station
State/province/country: Amsterdam, Netherlands
Your status (Gold/Diamond) at time of stay: Diamond
Type of breakfast offered: Full breakfast in lounge or restaurant. Breakfast in lounge included made-to-order eggs and pancakes; breakfast in restaurant included made-to-order eggs and (I believe but am not certain) pancakes.
Taken in restaurant or lounge?: Ate in lounge first day; ate in restaurant after that.
Extra options (e.g., upcharge for full breakfast): No additional charge for buffet in restaurant. Front desk stated that Gold would be eligible for full breakfast in restaurant at no additional charge.
Added your report to wiki?: added to wiki.

The only change from lmsalman's report is that the lounge has a full buffet, offering at least two types of hot meat, scrambled eggs, and cooked-to-order eggs. However, the restaurant has many more offerings, both hot and cold, as well as opening 30 minutes earlier on weekdays (and maybe on weekends).