There are many new features in .Net 3.0 that are major releases in themselves. Things like Windows Communication Foundation (WCF, formerly Indigo), Windows Workflow Foundation (WF), Windows Presentation Foundation (WPF), and Windows Cardspace.

Out of this menagerie of technologies my personal prediction on the most influential of these, or at least my favourites anyway, would have to be WCF and WF. The reasons I believe for this are:

• WCF is long overdue. We have needed this type of functionality for some time now and have managed to hobble along using similar technologies like WSE1/2/3 but they are simply not as fully featured, not as integrated, not as robust and not as efficient as WCF. I see this as an essential backbone technology to distributed systems that brings what is currently still a very complex and diverse way of interoperating, into a cohesive development experience. I would love to be able to use WCF in place of a mix of COM+ and WSE3 type implementations. Security is one aspect of this but WCF brings so much more to the table.
• WF is what everybody does in their apps, whether they like it or not. It makes all the common tasks of todays business apps quite easy to implement in a robust and scalable way. Kinda like making the boring, exciting again. A lot of time is spent designing ways of orchestrating workflow, even in simple apps, persisting that state, and various other mechanics necessary to make your app work. WF will do this for you, and it will include pretty pictures too. What more can you ask?
• I see Windows Cardspace as a sleeper technology. It is another technology that is more than overdue, but it is also one of the most sensitive areas. Peoples identities. I don’t pretend to have looked into this in detail, but you can be sure that there are plenty of people who will dissect this to the n’th degree, and with good reason. Hopefully, it will deliver in its promise, but I think it will take somewhat longer than the other technology sets.
• WPF is a great technology and many of my colleagues have embraced it with gusto. I am no UI designer though. Give me a design and I’ll code it, but give me a blank slate, and I’ll make it look like a typical developer interface. Ugly but functional. Give me WPF, and it will still look ugly and be functional, but it will have reflection, gradients, and be written in XAML. As an ASP.NET MVP, the move to a declarative style syntax with similar constructs to HTML is a welcome one, but I think the most influential technologies are still the ones I have listed above, while the most visible will be WPF.

Well that’s my opinion anyway. Would love to hear others.