As a Diamond, I was upgrade to a suite once and got partial ocean view room in Premier Tower rest of time. I got either Giorgio Armani Acqua di Gio or a bottle of champaign/wine except for the first stay when I got both.

Among Hyatt, Westin and Sheraton, Hilton tends to offer lower rates and one of the best rate is breakfast and dinner rate. At $169 or $159 prepaid, it comes with daily breakfast and dinner coupons at its Island Terrace restaurants. BTW, it servers only buffets but its dinner buffets are good. There is a different theme each night and cost ranges from $29 to $39 depending on theme. Dining is on expensive side in Guam.

As pointed out by others, Diamond treatment is not over the top but decent. It has very large gym (perhaps the largest among Guam hotels) and nice pools. The executive lounge is good and offers good breakfast but the hot evening offering is strictly fried items; French fries, onion rings, cheese stick along with cheese & veggie trays. Like other Guam hotels, alcohol beverages, beer and wine are complimentary.