Would a shop online accepting just Bitcoins work. Could be selling different products... or would people not really be interested in spending their Bitcoins this way?
It all depends. There are Anonymous VPN hosting and web hosting services that only accept bitcoin and are growing and doing quite well.
Coinabul accepts only bitcoin for payment and thus doesn't have to mess with the banking system, which for a relatively low margin business like precious metals / bullion, that is important. They seem to be growing as well.
SatoshiDICE, for instance, of course has no option -- they exist only because they accept bitcoins.
For other businesses, limiting their customer base to only those customers that will pay using bitcoins is a real handicap. A business that focuses on its customers generally tries to avoid barriers that make it harder for a customer to hand over money. So when it makes sense, bitcoin can be offered as one of multiple payment methods for the sites customers.
If there are higher costs due to chargebacks with credit card, then the service can provide a discount for purchases paid for using bitcoins so that those paying with a payment system that carries the risk of chargeback have the option to either continue paying for that convenience or save a little money and pay using bitcoins (by taking the discount offered.)
