I think a lot more people buy btc to buy things online than you would expect. That recent MIT study showed that the largest percentage of bitcoins purchased nowadays, are spent within the first 24 hours.
In regards to overstock.com, those numbers are pretty good, but they have dropped steeply from the larger numbers they were putting out in the first few days...
agree, its convenient for me to keep some bitcoin on my chrome addin wallet, makes shopping super fast and easy