Finally had a chance to give it a quick spin on the mac. macports doesn't have the latest 0.8 version, yet, so I had to play with 0.7.1.

First attempt at running it, I got a thread error and a crash. Second time running it, it started up fine. I didn't have time to import a huge swath of images, so I don't know how well it handles large libraries. The single image I did import let me poke around. The UI was reasonably self-discoverable, but there were a few aspects that were non-intuitive (getting back to the the light table mode, or whatever it was called, from the editing mode, for example), and I can't help but feel that, with my one-button mouse, I'm missing some context sensitive menus.

As for the image editing aspects, it was quite responsive (and the next version is supposed to have 5-10X speed improvements). It has all the basics that I'd use regularly (white-balance, exposure control, sharpen, denoise, etc), some intermediate plugins that I'd use every now and then (zone system, lens correction, etc), and some plugins that I look at without the foggiest clue what they do (okay... they're for colour correction, but I don't know why I'd use them, let alone how to use them, or an understanding of their effect).

On the whole, I'm quite pleased with it, and at this point, I'd have a hard time justifying the expense of Lightroom, particularly since I heard about it from a fellow who switched from using Lightroom to use this.