Actually, Caslance, this is big news, not least because it is also expected that CEA will be one of the airlines coming together to order the 7E7. That said, the 333 is considerably larger than the 7E7-8, so there's not a conflict between in them in terms of capacity.
As regards the 330 program, this is one of the largest orders to date; I would imagine it's the largest single order for the 333; other airlines, like CX, operate more, but have acquired them in smaller numbers over the years.
The new aircraft will replace, among others, China Eastern's A300-600 fleet and will provide standardisation to the medium haul fleet after the merger with some of the regional carriers.
CEA is the first customer for the 333 in China, although China Southern has about four A330-200s on order. Not sure when the first one is due.
Incidentally, I believe the first Airbus delivered to China was an A310-200 delivered to the then CAAC in the late 1980s and operated by the Shanghai directorate, which ultimately became China Eastern.