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You will be able to run 11g on a cluster of non-Unix machines. For example you could string together a couple Intel machines and spend less money. Conversely you can run 11g RAC on a single machine, and still take advantage of RAC features.
11g R2 has new and improved data compression. Anything that saves disk space is a good thing in my book as long as it works correctly. Finally you will be able to do a hot application upgrade in 11g without shutting down the system. That's hot.