Other than Razor (which is optional), not that much has changed and it is a pretty painless upgrade. Under the old way they used to version software, this is really more like ASP.NET MVC 1.5 SP1
The other thing worth noting is way better support for dependency injection, through the DependecyResolver class. I'm becoming particularly attached to the IViewPageActivator interface for providing custom view creation logic (in my case, injection of helpers and custom session information into the page object).
Heh, sure it's optional but if you stack it up next to the TERRIBLE Web Forms syntax...
Well if you were using Spark already, you can go to v3 without changing your templates
Spare a thought for those of us who have to maintain ASP.NET 2.0 Web Forms apps for a living.
I know! They iterate pretty fast. I love it but it's hard to keep up