“I think this guy is going to be a real winner,” said Bill Atkinson, holding up what looked like an Apple (AAPL) iPad tablet computer before an adoring audience at Macworld Expo.

It was only a cardboard mock-up, created to show what his latest project — Bill Atkinson PhotoCard — would look like on the new device.

But he had clearly spent some time playing with the real thing and come away impressed.

“Its not a laptop, it’s not a smartphone, but once you pick it up, you’re not going to want to put it down,” Atkinson said. “I think Apple’s got a hit on their hands.”

Atkinson played a key role in the development the original Mac. He wrote MacPaint, one its most popular applications, and designed and implemented both Quickdraw and Hypercard. He left Apple in 1990 to co-found General Magic, which created one of the first hand-held personal digital assistants.

In 1996 he returned to his first love, fine-art nature photography, which led to PhotoCard, a $4.99 app that allows iPhone users to send jumbo-sized stamped postcards made from his photographs for about $1.50 apiece.

[Follow Philip Elmer-DeWitt on Twitter @philiped]