Unity's Tom Higgins announced it on the blog : on March 19, after a whole year of hard work, Unity 2.5 was shipped with, as the key improvement feature, support for Windows (XP and Vista) authoring.

Driven by the reality of the market, or by the need to make (another) difference among competitors, Unity finally decided to get rid of what used to be considered one of its major drawbacks and propose a fully cross-platform development framework.

Other improvements include (complete list here) :

• 3DS Max importing
• tabbed interface
• precise navigation and placement tools (snap and similar)
• customizable editor
• improved usability
• Google Chrome support

As they expect, "it’s going to be an exciting year". We truly hope they're right!