One way that you can tell that a product is getting more mature by the type of features that are included with new release. By this measure, ASP.NET is getting to be positively adult like.
I just sat through the session on ASP.NET 4.0 futures. The main announcements are surprisingly tame. Well, surprising by former ASP.NET standards. And not particularly revolutionary.
There are, of course, other reasons for that. The ASP.NET team has been working on a release schedule that is based on Internet time. In other words, you can't want for three years between releases when the rest of the world is innovating every 6-9 months. That's one of the reasons that you saw an MVC release onto Codeplex. It's why you saw Atlas before AJAX. And why the AJAX Control Toolkit exists.
As a result, the advancements are more along the lines of incorporation and integration of these features. MVC is officially part of the product. As is the AJAX Control Toolkit. All good things, but definitely not earth-shaking.
There are a couple of changes on the technology side. There is support for JQuery, a JavaScript library used to improve the integration between JSON and HTML. The binding used in AJAX looks much more like the WPF binding syntax. That last point made me wonder how long until there is a convergence of ASP.NET and WPF, when it comes to application markup.
There are a number of other announcements, regarding JavaScript integration, better granularity when it comes to enabling and disabling ViewState (yeah!), and more control over how server controls deal with CSS markup. If you spend your business hours working with ASP.NET, some of this will probably fall into the 'finally' category. But for me, there was nothing that I found particularly compelling.