Hi dreamcatcher,
The experiences that our members have with alibaba.com may vary from one member to the next as some may have found great suppliers while others may just have been scammed. We suggest that if you indeed decide to use the suppliers you mentioned, please do with extreme caution.
We do have several posts made by our members here in the forum and SaleHoo has written a blog particularly about Alibaba.com, here's the link to the blog:
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Here are a couple of posts for your reference:
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You can actually search for more posts by using the 'Search Forum' option on the side menu.
Hope this helps! Cheers :)