The firm doesn't yet have enough stock to let its stores sell the smartwatch, and many shoppers who tried to pre-order the device online in the initial hours after it went on sale a fortnight ago have been told that they must wait until May or June for their deliveries.Those who do receive the first batch today will only get a taste of the Watch's full potential. For now, most third-party apps will depend on a wirelessly-linked iPhone for processing power because Apple hasn't yet allowed them to run natively. "We are raising our Apple Watch shipment estimates for 2015 from 17 million units to 20 million units, as we estimate sales of over two million units during the pre-sales phase alone, and believe watch revenues could contribute as much as 8% of [Apple's] total revenue in 2017," wrote Daniel Ives from FBR Capital Markets in a note to investors earlier this week.