True to its word, Aspyr Media put Duke Nukem Forever on the Mac in the month of August, a short while after the game's release on PC. You can pick up the title at GameAgent through Aspyr's website, or on Steam (where you get it, thanks to SteamPlay, for both Windows and Mac), but if you want to go cheap, MacUpdate is running a promotion where the game is $5 off the standard price, and you'll get Jets'n'Guns Gold for absolutely free as well. That's about the best deal I've seen, if you're planning on buying the game and don't mind where it comes from.
Be warned, of course, that the critics didn't really enjoy the long-awaited title all that much, claiming that the design showed its age and depended a little too much on the game's reputation rather than actual innovation. But that hasn't stopped the game from being a financial success anyway, and odds are that if you're a Duke fan and just want to play the game, you're not that worried about how it stands up to the test of time. Hopefully you're low on your supply of gum, because Duke is ready to get back into action.