I'm a little bit saddened to see this reaction, as Damien is one of the "good guys" who has made this available for free (although a paid version is now on the horizon). More importantly, the code is open-source.
There are several practical issues Audirvana addresses on OS X, which I will list in a somewhat subjective order (i.e., of importance to me).
1. The single biggest problem with iTunes is its inability to switch sampling frequencies on the fly. If you have Audio MIDI setup set to 44.1kHz, and use iTunes to play back red-book or most iTunes-store-provided music, it can do so with bit perfection. However, if it then meets, say, a 96kHz track in your playlist, it will downsample it to 44.1kHz on the fly during playback, unless you manually quit iTunes, manually reset Audio MIDI Setup to 96kHz, and then re-open iTunes. Audirvana (and several others, like Decibel, Ammara, Pure Music, etc, also will do this). This is primarily a technical advantage, but for those who take bit-perfect playback seriously, it avoids a potential degradation of sound quality.
2. It permits playback from memory. The entire file is decoded (and uncompressed) into memory, assuming sufficient memory is available. To enable seamless playback, the n+1 track is also cued into memory. Audirvana is not unique in being a memory player, but it has what is arguably the sanest implementation.
3. Like several others, it has the option of hogging the output device. This can be fairly critical, as Apple by default wants all applications to share the output device, so that you will be able to hear all of your mail arriving from Nigeria during playback of Beethoven's 9th. The resulting mixing, in addition to being an irritant, results in resampling the audio, again potentially degrading sound quality. Hog mode prevents this, and integer mode, available in 10.6 but not 10.7, in addition permits skipping two arithmetic operations, converting back and forth between integer and floating point, which are unneeded operations when one application is hogging the output device. I personally cannot hear any difference, but others claim to.
4. It can play flac, unlike iTunes.
5. It can up-sample more intelligently than core audio. Apparently, some DACs have a sampling frequency sweet spot, and this helps. I have never used this myself.
6. You can easily assemble temporary playlists on the fly (and you can also save them). (I seldom make playlists in iTunes because it is so cumbersome.)
There are a few others, but 1-4 and 6 are the most compelling to me, and having this available as an open-source project is an added attraction.
I've written a few Applescripts and an iTunes plug-in to enable using iTunes and its associated Remote.app with Audirvana, which are also available for free. (google nyquist.zsh ).
In any case, it is an application not without merit.