Emirates is already that largest user of 777s in the industry, with 94 in service. This order, for an additional 50 777-300ERs has a value of over $18B. There's also an option for 20 more, adding another potential for $8B more to the deal.
Perhaps this is an indicator of things looking up in the industry, if not the global economy in general. With this order, Boeing has broken it's 777 annual sales record, set back in pre-slump 2005.
http://money.cnn.com/2011/11/14/news/companies/boeing_emirates/index.htm?hpt=hp_t1