The system it is running off of was built from scratch in Rails, with a PostgreSQL backend. We are also heavily relying on Apache Solr (and the acts_as_solr plugin) to power our product browse / search pages, and use it to provide some very cool faceted search capabilities.
I applied for YC funding two years ago with a different idea and got rejected (for valid reasons). We did not apply for funding with this startup for two reasons, one was we did not need external funding, we have been able to bootstrap this far. The second reason was we wanted to stay in the Philadelphia area, our industry connections are here and we are also opening up a retail store. So since this is not a purely tech startup, the benefits of being in the valley or Boston are a bit less.
Please give us some feedback on what you guys think, and if anyone wants to chat about implementation or other specific details drop me a line, my email is in my profile.