The list of changes from MVC 2 and MVC 3 is rather extensive. We're excited about working with it too. Here is the complete list.
• Extensible Scaffolding with MvcScaffold integration
• HTML 5 enabled project templates
• The Razor View Engine
• Support for Multiple View Engines
• Controller Improvements
• Model Validation Improvements
• Dependency Injection Improvements
• NuGet Integration
• Partial-Page Output Caching
• Granular Control over Request Validation
• Extensible "New Project" Dialog Box
• Template Scaffolding Improvements
• New Overloads for "Html.LabelFor" and "Html.LabelForModel"
• Sessionless Controller Support
• New "AdditionalMetadataAttribute" Class
• AccountController improvements
• New Intranet Project Template
These features will indeed change the way you write your code, The most affected seems to be the View part as represented by the new Razor View Engine. The Scaffolding support is really nice. From a pattern perspective the Dependency Injection Improvements may change some of the code, but probably not that much.
Looking at the overall.NET Web architecture the MVC 3 upgrade is primarily a change in the View (and Controller to some extent). Anything else, such as the Model, DTO's, Service Layer, Data Layer, etc are all unaffected.
We are working on updating the Design Pattern Framework with MVC 3 and the new Entity Framework 4.1. However, there is no official release date as of yet.
Hope this helps.