"36 hours later still no redemption code for mountain lion, a phone call to apple informed me the process can take up to 72 hours?? Huh?" tweeted around 5 p.m. PT Thursday.

"A day and a half later and still no Mountain Lion redemption code. This is what a Retina MBP earns me? Frustrated!" said , referring to the MacBook Pro equipped with a higher-resolution display.

Blackwood and Derrick were joined by scores of others also on Twitter who complained about Apple's inability to get them the redemption codes they needed to download Mountain Lion.

Last month, that if they purchased a new Mac on or after June 11, they were eligible for a free upgrade to Mountain Lion. The program, called "Up-To-Date," started taking requests from those Mac owners Wednesday when the company shipped Mountain Lion to the Mac App Store.

The terms of the deal, as spelled out in the fine print on the , promised a code would "be emailed within 24 hours of order qualification." The phrasing, however, distinguished between that "order qualification" and the customers' submission of a request.