Broadsword Online Games have released Publish 97 for Ultima Online onto the Test Center shard. The main focus of Publish 97, at least for now, appears to be pets:

Included in this first release of Publish 97 is the much-anticipated pet revamp.  Make sure you patch up to the latest client before heading over to TC1.  We had several core goals going in to the pet revamp with regard to pets including,

• Ensuring the Greater Dragon is still a viable pet for those that have and wish to continue to use them.
• Allow greater diversity of pets that are effective by looking at their survivablilty and allowing animal tamers to customize their pets to increase survivability and variation.
• Provide an in-game path to learn to use Animal Training with as much information as necessary to make Animal Training something everyone can have fun with.

In order to achieve these goals you can look forward to the following changes with pets,

• Pets can now be trained beyond their current control slot requirements up to new maximums.
• Train pets in endless combinations of special abilities, special moves, area effects and magic schools.
• Customize skill caps and attributes to create new pet variants.
• Read the full initial release notes here

This is only the first iteration of Publish 97 and at this stage we want to concentrate on testing the Animal Training process.  This includes the in-game path for learning about this new feature, as well as your experience with training pets, the results of customizing pets, and how those customized pets are balanced with the rest of the world.

And already, after only a few days, there has been an update for the Publish released:

We have updated TC1 with the latest version of Publish 97 which includes the following changes,

• Adjusted the training scheme for pets involved in the training process. There is now a Guaranteed Gain System as well as a greater chance to gain at lower levels of progress.
• Now provide additional feedback to players when their pets gain battle experience, or fail. The messages on TC1 are currently placeholder and will be updated before final release.

Full change notes for Publish 97 can be found here, and feedback concerning it can be submitted here.