This is from the press release

Wider Platform & File Support: Virtools 4.1 and 3D Life Player are now compatible with Microsoft Vista and 3D XML V4. In addition, the Virtools SDK is moving to Visual Studio.net 2005.

Improved Usability Enhancements to Reduce Production Time: One much awaited feature for Virtools is the ability to instantiate a behavior graph that is introduced through a new "Call Behavior" building block. Using this new feature, developers will be able to considerably improve production workflow and delivery time.
Virtools 4.1 also provides rich ergonomic and schematic improvements as well as new commented video tutorials, significantly shortening the Virtools 4.1 learning curve.

Simplified Virtual Reality Production Capabilities: Both the Virtools VR Library and the VR Publisher model have evolved to respond to VR community feedback. The simpler publishing model is now available in two versions: "classic", targeted to mainstream VR displays (simple stereo HMDs or Walls) or "unlimited", supporting higher-end systems, including multi GPUs or clusters. This new VR Pack 2.5 also provides better clustering support, improving synchronization performance and quality when using Nvidia Quadro Fx G-Sync hardware, and better supporting multi-pipe and multi-core systems. It also includes new ready-to-use application templates (VRNR), provides support for recent VR devices like Natural Point Optitrack and Xsens MTi/MTx, and adds numerous development and deployment time-savers. New demos have been included, enabling new users and integrators to even better demonstrate the power of their VR equipment.

Enhanced Artificial Intelligence Capabilities: Partnering with Kynogon, Virtools 4.1 provides integration of a new AI library 2.0, which simplifies path-finding generation and design of Non-Playable Characters’ behaviors.

Looks like they addressed some interesting aspects. Personally I only heard negative things about the older AI pack. Hopefully this new iteration is useful. The VR Pack license scheme was also weird. I wonder if the new approach has an effect on costs. I also wonder what they mean with better clustering support. I am currently helping with probably the biggest Virtools cluster in the world and in our case more functionality for controlling and debugging the cluster is needed.

The BG instance thingy is very interesting - I hope it works well with tracing/debugging. I also hope we get our "center to BG on closing" 'rich ergonomic' feature. Anyways, much too early to do any serious commenting on it - it's just I don't write a lot on my blog recently so putting the press text without any 'blahblah' comments sounded like a bad deal.

p.s. more details are now available on the virtools site .