The LINQ Project is probably the most exciting announcement of PDC for me.
I have been using an O/R Mapper for quite some time and I couldn't imagine designing a new application without using one.
We all heard about ObjectSpaces way back on 2002 and how it would bring object orientation to relational database UIs. Then we all wondered what happened to it when they decided to pull it from the 2.0 Framework. Well, the ideas of ObjectSpaces were rolled into an even more ambitious project, that is LINQ.
LINQ is broken into several Namespaces: DLinq, XLinq; which target SQL and XML specifically.
LINQ will not render tools such as LLBLGen useless, in fact, it will further enhance what they do best and allow them to focus on how to do the mapping, LINQ will provide a unified approach to provide the plumbing while third party tools can focus on doing the mapping for us.
Then using LINQ we can interact with our data in a very object oriented way that is standardized across implementations and does not require us to remain dedicated to a 3rd party solution to provide proprietary ways to actually do the objectness.
One of the biggest gripes I hear from people about XML is how hard it is to understand and implement things like XPath and XQuery. XLinq and DLinq are going to unify the way we interact with persited data in either XML or SQL, we will essentially access them both in the same way, this is HUGE, it removes the ramp up time developers will need to be able to intuitively write programs that need to interact with data.
As the project progresses, other persistant data will be added so that we can interact with things like the Registry, WMI, LDAP and other structures in the exact same way without having to learn the internal plumbing required to do that sort of interaction.