I like several things about alibaba.
The messaging subsystem works very well. Sometimes it is a bit slow, but I am literally on the other side of the world, so it's ok if I have to wait for a few seconds here and there.
The trade assurance is great for trust in the business.
Some providers have been checked on site. This is a great feature, so you know you're dealing with a legit company.
Tip for consumers: check that your providers are legit by going to their description within Alibaba. Trade assurance is free, so use it.