With the announcement of the .NET 4.0 exams, it seems a bit like a wrong career move not to aim for taking the web application development certificate for 4.0 instead of 3.5, since I have already been working with VS2010 for some time now.
Looking at the Skills Being Measured List it seems like a good idea to continue studying the MCTS Self-Paced Training Kit (Exam 70-562) with a sharp eye to the list of topics.
Hopefully I will be invited to take a beta exam when they come out in April.
I guess a good place to start looking into the ASP.NET 4.0 would be here
Here are some of my comments to the elements of What's new: