Wow, there's a lot of unhappy people here. Let me tell you my latest experience.
I have a Platinum subscription ($10/mo), which gives me a better rate on shipments. Still, on my last shipment, the usabox packers saved me almost 50% of the initially estimated price, by repacking everything to save on space.
So far, the support at usabox has been responsive when I had issues, like when a duplicate package appeared in my Inbox.
A word on volumetric weight (an issue for some): carriers measure a package's "weight" by taking either the real weight or using the sum of dimensions, whichever is bigger. Thus, several individually packed shipments will always be more expensive (due to padding) than a single repacked shipment.
The 4 stars rating is because there is room for improvement. Keep up the good work, guys!