"Excellent interface"
We have built a streamlined interface that is uniquely designed to handle grocery shopping. We believe that there is a fundamental difference in shopping for groceries online and the way we shop for other consumer merchandise (such as clothes or books). Being fast, intuitive and discoverable are the overarching goals.
"you should seriously consider delivery"
At a later date, perhaps. "Logistical nightmare" is absolutely right. When/if we do delivery, I want to treat it as an outsourced add-on priced at/near cost (which will still mean a hefty delivery charge in low population density areas).
"I also love the possibilities for the store itself"
Absolutely. In addition to your suggestions, consider the long-term opportunities related to merchandise packaging and private label goods. Customers are no longer walking the aisles making buying decisions based on physical packaging. The right packaging/private label strategy (think Trader Joe's on steroids) could eventually lead to some amazing gross margins.