The first one is to validate that Bitcoin actually makes business sense for us to accept - which I obviously believe it does, and will be proven out by sales. I've already done the hard job of explaining to all the key people what exactly Bitcoin is, how it works, etc - and while they don't necessarily get the nuance of it, they love the principle of it, which is why we're doing it.
The second issue is a bit trickier, and that is actually holding BTC in it's BTC form - for a larger company, it's an accounting nightmare... I spent a fair amount of time with our interim CFO playing around with different scenarios, but from a GAAP standpoint it's a no go.
Now, that's not to say that we might not be able to issue payments, etc in BTC in the future (even the near future), but more than likely we would do it by spot-purchasing the BTC, not actually holding it on hand. While it means there is some transaction cost to doing it, it would be transparent to our users and wouldn't cause the bean counters to have nightmares.
I like your suggestion though about at some point allowing the consignor to opt into getting their payment in BTC - in that instance, we could only convert our percentage to USD, and just transfer the BTC portion to where-ever they like. I hadn't really considered that, but it's a great idea.
The funny thing is that quite a few of our employees are pretty excited about us supporting BTC, and want to get a portion of their paycheck in Bitcoins - which I also think is pretty cool.
Right now we use Bitpay as our payment processor, and their API is dead simple, but to be fair, after integrating with places like eBay and Amazon, places like Mt.Gox are a piece of cake... Right now I'm really focused on making sure that the buying side of the equation really works smoothly (for both us and the buyer), so I'm more than happy to give them 1% to not have to worry about any kind of regulatory issues (since they're a pure merchant services provider).
The cool thing I think we bring to the Bitcoin community is the shear size and diversity of the things we carry - each store averages about 100,000 unique items at any given time, and typically adds about 2,500 new items per week. Right now we have two stores, but we plan on opening a third in Las Vegas before the end of the year (it might not be opened by then, but we'll have the building locked up, and be busy doing the TI to bring it up to spec for us). Our longer term goal is to open 20 stores in the next 3 years, so assuming we can maintain that, we'll have a TON of things that people can buy, and lots of physical locations that they can even come down and check things out.
Let me know what you think, and what you'd like to see from us as a retailer... Right now my focus is on getting Ultimate Consignment supporting Bitcoin, so once that's done I'll be looking at how to better integrate it I'll look at enhancing UL as well.