My Mac photo editor of choice, Pixelmator, has been updated to version 1.6 just recently. It's mostly a performance update, adding performance and bug fixes, support for 64-bit architecture, and a whole lot of polish for Snow Leopard. Additionally, they've redesigned the transforming tools, added an import feature (to bring in images from a camera or another source), and added the ability to send out photos directly from Pixelmator to Facebook, Flickr, or Picasa. That's pretty slick.
And of course this is a free update for registered users, so you can install it from right within the app. If you haven't picked up Pixelmator yet, you can get a license for $60 -- not exactly cheap (or free, if you're a Gimp fan), but when you compare it to another full-featured editor like Photoshop, it's quite a bargain.