I have bought from their Spanish warehouse and it did work great with no issues regarding customs, which is a major headache in Portugal, because every item pulled to customs will be retained for weeks or even months.
I think they have arranged some dubious way of getting stuff out of the harbour without declaring it. Popular items get stocked, others won't.
Also, they ship to some countries, where the item is put in a new envelope or package and shipped from a EU country. Example: China to Switzerland, repackage, Switzerland to Portugal. The Swiss are not members of the EU, but they have Schengen. This makes control dubious and he'll, the Chinese know how to make use of this...
Gearbest is well known and recommendable.
Regards,
Vitor