From Wikipedia:

Seven Stars - The highest tier, requiring 100,000 tier credits. Members are not automatically enrolled as they must be invited by their casino host. Some qualifications, aside from tier credits, include not having any outstanding markers (credit), and not being a security issue at any Harrah's property. Guests at this level are the priority for all casino workers. Seven Star guests are provided with priority lines and first available service at participating Harrah's Entertainment properties. Seven Stars members are also entitled to up to four nights complimentary at any Harrah's property, given at least 48 hours notice is provided. Also, Seven Stars receive 25% off spa services, and complimentary entry into spas and health clubs at Harrah's, as well as gift shops. These guests are also entitled to one free trip to any Harrah's property per year. Included is complimentary airfare, hotel stay, food, and television viewing. Alternatively, they may also take a complimentary annual cruise. All Seven Stars guests are entitled to complimentary hotel stays and television viewing (including adult entertainment) at any Harrah's property. Also, they are entitled to a birthday dinner at the property and restaurant of their choice, with up to three additional guests. Furthermore, they are entitled to one complimentary spa service per year, up to $100 in value. There is also a separate booklet of merchandise only available for purchase by Seven Star guests, including luxury automobiles. Finally, all Seven Star members are eligible to have one companion member per year. These companion members are entitled to the same amenities as a regular Seven Star guest. However, they are excluded from redeeming the annual trip and other larger amenities. Other perks vary from property to property, due to the further integration of the Total Rewards system in all the properties.

For me, the most valuable is the birthday dinner and the free trip to any US Harrahs. I flew (1st class) to New Orleans and San Diego on my blue card. French cuisine at Guy Savoy at Caesars Palace is the the best you will find in Las Vegas, and maybe the best this side of Paris France. The annual gift is outside your stash of player points and you get to pick it from a special list. There used to be a very nice Seven* lounge at Caesars Palace but was closed as part of the general cost reduction programs.

I am back to Diamond this year as there are few decent video poker plays at any Harrahs property any more. You do get superior attention from the staff of the casinos when you present the card. I got several calls from casino management to see if there was anything I could suggest to improve service. I suggested they get more cocktail servers in Caesars casino .

A couple of times, when I visited a competitor's casino and showed them the Seven* card, they gave me to top tier card from their casino to play on. The Hard Rock in Biloxi was an example. There may be better perqs from other casinos but the 7* card seems to be the best known and most recognized.