I have made about 90 orders without problems. If I had a problem, i have got very quick refund. All the sellers benefit from their reputation, so they don't want to get bad references, because AliExpress will cancel cooperation with them or the people will stop buying from them.
It's all about expectations. If you buy a "jewelry" for 1USD, don't expect Swarovski, but it could be nice for kids. Clothes are in general very good quality, just be careful of sizes. Especially the small things are reliable like toys, key-rings, T-shirts, towels, etc.