Piper Jaffray analyst Gene Munster today issued a new research report sharing data from research firm NPD covering Apple's U.S. Mac sales for the month of January. According to NPD's data, Mac sales were up a strong 31% year-over-year for the month. Munster attributes the strong performance to Apple finally being able to roll out orders of the new iMac, even as the company remains significantly constrained with multi-week waits for new orders through its online stores. Apple announced the new iMac in late October of last year, but did not begin