Mac shipments are up, rising 25% in May compared to April, and Apple's new MacBook Pro units are a "catalyst for growth," according to Morgan Stanley analyst Kathryn Huberty. Ms. Huberty's analysis is based on numbers from NPD and from comments from unnamed suppliers.

"Even before the new MacBook Pros launched," she wrote in a research note covered at Fortune, "Apple began to outperform the broader commercial PC segment -- with commercial Mac shipments up 25% [month over month] in May versus market growth of just 1%."

Ms. Huberty raised Mac unit sales estimates for the just-ended June quarter to 2.5 million from 2.4 million, adding that she expects Mac sales to add US$1.16 per share in revenue for the quarter.

The analyst has a mixed record in covering Apple. For instance, in September of 2008, she cut her rating on Apple because the company wasn't strongly positioned in the el-cheapo market where netbooks were all the rage.

Apple still isn't in the el-cheapo market, still doesn't have a netbook, and has outperformed the market in PC unit sales both before and since that rating cut in September.

In the meanwhile, AAPL rose in mid-afternoon trading, and is currently at $143.27 per share, up $0.84 (+0.59%), on moderate volume.

*In the interest of full disclosure, the author holds a small share in AAPL stock that was not an influence in the creation of this article.