Modul8 has been one of the premier VJ applications for Mac OSX since version 2.0. Following is a review based on extensive use up to the latest version, which as of this review stands at 2.5.2.
Pros

• Ability to use native OpenGL Core Image and FreeFrame plugins.
• Extensible, highly-programmable user interface.
• Excellent keyboard and MIDI mapping.
• Can use multiple video cards to span video across multiple screens.
• Good learning curve.
• Plenty of preview options.
• Frame-accurate rendering to disk.

UPDATE: new version ES-X 1.2 released
Here we go: ES-X 1.2 for Mac and Windows has been released, so its time to take a look at the new features and to bring this review up to date. Videokonferenz has brought some very usefull additions into this new version without breaking the paradigm of ESX - flexibility and ease of use. Many of the bugs present in the 1st version have been fixed and the performance has been improved dramatically.

So what's new?

My absolute favorite is the new live video input with frame buffer of 160 frames:

Modul8 offers ten fully adjustable and scalable layers to composite and position in a variety of different ways. The best thing about Modul8 is that its geared towards transparency and ease of use. It wants to be instrumental and based on playing, not thinking. I enjoy mixing with Modul8, not just the end result, I dig the process of getting there, too.

Veejay is a video tracker/editing and live performance tool for Linux. It provides a graphical interface for video editing and mixing as well as a keyboard interface for direct user interaction (in a performance environment) ...
General

* Free Software (GNU)
* OSS audio
* SDL/DirectFB output
* Man pages/HOWTO
* console interface 'veejay'
* graphical interface 'gveejay'
* Samplelist load/save

Media

* MJPEG codec
* Quasar DV codec
* YUV4MPEG
* Video4Linux devices (webcams & capture devices)

* vloopback devices

I don't know how many of you actually purchased MD3 but if MD4 is anything to go by, then don't be too seduced too early by the amazing packaging. Digitalstage have employed some nifty art graphic bods and I love the presentation, in fact maybe the packaging is too sexy! I spent too much time with the stickers, free demo dvd and posters which suggests this is no deep profesional tool....style over content? Should you be worried? Read on.

LairWare's Pixeltoy basically makes cool color patterns, particles and effects similar to what you would expect from most audiovisualizer programs, but adds an intuitive programming interface and lots of in-flight control. The results are very nice looking and it's surprisingly easy to customize and save your own patches and color sets to invoke at the touch of a button. If that sounds fun or useful to you then it is definitely worth the $20 shareware fee.

For those of you who know of the modular audio s/w called reason, you will understand the concept behind Elektronika easily.

It is a moduler VJ system. You load the generator and effect modules you require and then patch them together to custom build your own video system.