Having read many a complaint over the years, including the responses given by supplier representatives, if all goes well, then the experience can be good.
If something goes wrong requiring after sales support, there is a tendency for them to try and fob you off, give you incorrect or misleading information, pretend not to understand English as well as they should or make a quite ridiculous offer of compensation.
If ordering direct from China or similar territories, always factor in the import charges that your country may levy, as you cannot ever guarantee avoiding them and if using express air mail using a popular carrier such as DHL, then you can count on import charges (and in some cases an extra carrier levied charge).
Always use a payment method that can give you independent protection, such as Paypal.
These days you may also find a local stockist on fleabay, where large quantities drop shipped to your country can be sourced where import charges will have already been paid and where the cost might not be much more then ordering direct from Asia.
Also, as we have seen with the Hardkernel N2 warranty, check that your supplier offers a decent one, in line with your own nations policies.
Having said that, the returns process for sending things back to China can be a pain, as some vendors will not accept express deliveries, so you have to use snail mail that may give you less protection.
Always remember that China’s (and others) trading terms are unlikely to be same as your countries and your rights may well be close to zero, which is another reason to have independent payment protection.
Ignore ALL reviews on a Chinese vendors site as they often only publish 4 and 5 star reviews, most of which are likely to be false anyway, so take purchase advice from users and respected review sites.
Of the dozens of devices and boxes that I have received over the years, the majority have worked correctly out of the box (save for crappy firmware etc) and have lasted well.
Places like Gearbest and Geekbuying do seem to me to be rather more reliable than Aliexpress, where trading can be more like the wild west.