Mixed reviews

At Apple's flagship store in New York, Jack Weber, who was visiting from Charlottesville, Virginia, said he would give his wife a top-of-the-line "Edition" as a 50th-anniversary gift.

"What more perfect wedding present could there be than this watch?" he said.

Long wait times will likely stimulate more demand for the watch - which allows users to check email, listen to music and make phone calls when paired with an iPhone - with little risk of losing impatient customers, said JMP analyst Alex Gauna.

"You would want to catch up by the holiday season," Gauna said. "But based on what's out there in Android land, I don't think there's an extreme risk in near term of losing customers who must have a smartwatch and will go to some alternative."

Android is Google's mobile operating system used on many smartwatches.

Reviewers this week praised the watch as "beautiful" and "stylish" but gave it poor marks for relatively low battery life and slow-loading apps.

Sales estimates for 2015 vary widely. Piper Jaffray predicts 8 million units and Global Securities Research forecasts 40 million. By comparison, Apple sold nearly 200 million iPhones last year.

Apple's watch is widely expected to outsell those by Samsung, Sony Corp and Fitbit. It will likely account for 55 percent of global smartwatch shipments this year, according to Societe Generale.

"Apple will outsell its wearable rivals by a very wide margin but it will do this on the power of its brand and its design alone," independent technology analyst Richard Windsor said.

Apple shares closed 0.43 percent higher at $127.10 on Nasdaq.