I haven't any experience with vpost but I did order from an american company www.vitacost.com. As the order was quite large, I had to choose DHL to deliver the products.
Normally DHL time to delivery is pretty good. However vitacost's contract with DHL does not include on-line tracing of the delivery status of the goods. I suspect that DHL will handle the package until it gets to Spore, then pass it to Singpost for delivery. The package was delivered by Singpost. As a result, the package took 30 days to reach me.
I paid US$30 for DHL to deliever the products. The 30 day time to delivery is not acceptable:( As a result, I'm reluctant to re-order from Vitacost.