I just read a thread on Whirlpool about Alibaba and Aliexpress and the general consensous was that it's full of scammers. There doesn't seem to be any protection for buyers, so if the goods are faulty or don't turn up, tough luck. On the rare occasion you do manage a refund, it can take 7 months.

From a sellers perspective, it sounds like it's a place to sell bulk items as opposed to one off's, so might suit some of the higher volume sellers here.

http://forums.whirlpool.net.au/archive/1622257