Personally, I found it very useful for following stories as they were developing, or to see if other people were having issues with a service when I was. Having this integrated into my normal Google searches was convenient, but I guess using Twitter's search directly isn't terrible.

I am pretty sad that this contract is not renewed. I found Google realtime search ironically provided a much better search interface for tweets than the one twitter did.

Plus they already crawl Twitter. It may not be real time over all of Twitter but I bet the accounts with a great deal of followers get crawled every few hours.