This guy is using Adobe Flex as an OLAP client against Openbravo ERP data. He now plans to “connect Flex to [the Mondrian] OLAP server and let the OLAP sever do all the hard work”.

Sounds like a great idea: keep the big data on the server side, send just the multidimensional, aggregated results over SOAP (XML for Analysis), and let Flex do what it does best: fast, rich client.