I think the best example for a good site to use Bitcoin as a payment method is Overstock.com. For those of you who still don't know it yet it is like the Amazon version of Bitcoin users around the world, it even has better international shipping coverage compared to Amazon since they use a 3rd party (FedEx) to handle its shipping needs. What they do use to implement their Bitcoin payments is Coinbase Commerce but you don't necessary need to log-in to your Coinbase account nor need it as you can just scan the QR code after picking the Bitcoin option. But if I were to nitpick and suggest a better feature I think is of course having a cheaper shipping cost because some of their shipping cost (also depending on the seller)  considering how far you are are more expensive than the item you will be buying.