By Katie Marsal

Published: 04:00 PM EST

Microsoft Corp's ongoing struggles with Windows Vista are buying Apple Computer more time to strengthen the features in its rival Mac OS X Leopard operating system, one Wall Street analyst says.

At its annual developers conference on Monday, Apple poked fun at Microsoft while introducing ten of the features Mac users could expect in Mac OS X 10.5 Leopard, slated to go on sale next spring. Up until the conference, Apple had insinuated that Leopard would make its debut a bit earlier in the new year.

Shaw Wu, an analyst with American Technology Research, said he expects Microsoft will have to report another round of Vista delays after a number of stability issues were discovered in the latest beta of the software. He said Apple is likely looking to capitalize on that situation by stretching out its development of Leopard in order to add more unique features.

In a summary of Apple's developer conference announcements sent to clients on Tuesday, Wu emphasized Apple's decision to keep some of Leopard's features "top secret," meaning the company has yet to reveal its full hand.

"While we [found Apple's] announcements impressive, we believe there may be slight investor disappointment that Leopard will not ship until Spring 2007 and that Apple did not make more announcements," the analyst said. "However, we believe with Windows Vista likely further delayed due to stability issues with its latest Beta2 version and its 'look and feel' and feature set essentially a 'clone' of Apples's currently shipping Mac OS X Tiger, Apple is choosing to spend more time adding features unique to Leopard."

Also on Monday, Apple announced its Mac Pro desktops systems, which Wu believes are valued quite well when compared to similar offerings from other system manufacturers. "In our analysis, it is also very competitive with high-end PCs and workstations that cost $3000-$6000," he said. "We anticipate this product to sell fairly well in its key markets, including professional and high-end customers who have patiently waited for a high-end Intel Mac"

Wu also told clients he wasn't surprised at the lack of iPod or music-related announcements at Apple's developers conference. He's long predicted a separate music event will take place in either September of October.

The analyst rates shares of Apple a "Buy" with a price target of $75.