Already I'm seeing people falling into the interface vs. implementation mistake with LINQ. Because I think LINQ is a big deal, I'm going to put up a LINQ Wiki RSN, but I had to post this because it got under my skin so: The compiler does not translate your query into SQL! The compiler translates your query into an expression tree that is resolved by an appropriate implementation of LINQ. In other words, DLINQ will resolve the query into native SQL and use all the appropriate database indices and execution plan optimization and so forth, XLINQ will resolve the query appropriately for its new document object model, and LINQ will resolve it for native objects (I think in naming they made a mistake -- Microsoft should make it clearer that the "native object" implementation is just Yet Another Implementation of the interface).

I am looking forward to different implementations of the interface, perhaps with constraint-programming or fuzzy logic implementations. As to other database vendors, whether Oracle will implement DLINQ efficiently is a business, not technical, question. As for MySQL, that, too, I would imagine that the Open Source community will rise to the opportunity!