My apologies - I get this question a lot and I appreciate your interest!
I'm working 8-10 hours a day programming the next version of BeerSmith which includes the Mac version. My current schedule is to have a beta out early next month and then set the launch date once we have some of the initial test results. Since this is a complete rewrite of the program and I have a large user base, I'm not going to rush the release - I want to make sure it is right!
However, assuming testing goes well, I hope to have it out this Spring including the Mac version. I have not been talking about it much because I want to get into testing and find out what kind of shape the product is in before I commit to a launch date. However, if you keep an eye on the site I will have a lot more information about it coming as I get closer to launch.
Cheers!