I took a quick pass through comments on the blog this morning. Until Beta 1, I am going to focus on responding to platform/infrastructure questions and steer clear of feature questions.

Is the PSI backward compatible? Will code written against the PDS work against the PSI? How about PDS extensions?

Strictly speaking, the PSI is not backward compatible. That said, most of the PDS methods that still make sense in P12 have similar methods in the PSI. If you wrote to the PDS, your code won't change much.

When we started P12, we decided to improve Project Server's extensibility. In our minds, this meant moving to ASP.Net and fully embracing web services and .Net in our development. Project Server 12 is completely written as managed code. Our clients (Project Pro, Project Web Access) ONLY interact with Project Server through our web services = the PSI. We opted to use ADO.Net datasets in the PSI. ADO.Net supports typed datasets. In VS.Net 2005, this makes the developer experience really sweet with the PSI. You get full IntelliSense on the datasets returned by the PSI and changing a project/resource/task/assignment/custom field/etc. is as easy as changing a field in the dataset and passing it back to Project Server.

Here is the net. The PSI is a modern and very developer friendly set of services. We think that it is a big improvement over the PDS. We definitely recognize that this will create some migration pain for folks using the PDS. However, the enhanced functionality of the PSI will enable you to get rid of lines and lines of code (especially in PDS extensions) and move to a a fully supported set of PSI methods. We are behind the PSI as our long-term developer and extensibility story.

How is Project Server integrated with Windows SharePoint Services? Is the integration better than in previous versions?

In P12, Project Server is tightly integrated with WSS. The Project Web Access UI is now a WSS application. You can fully customize and extend the PWA UI using the WSS webparts features that you know and love.

Server set-up, configuration management, authentication, backup/restore, monitoring, etc. are all shared services used by WSS, Project Server, SharePoint Portal Server, and the other Office servers. This is incredibly cool as it allows you to manage these servers together as a single farm. IT activities like dropping a new server into a farm are incredibly easy using the shared infrastructure.

I came to the Proj group from the BackOffice Server team in 2000. In Office 12, we are really delivering on the vision and dream of BackOffice = provide IT pros a unified, common set of tools and services for developing and managing applications built on the Microsoft platform. See us at the January Project Conference and I promise that you will see some great demos of this infrastructure at work.