It can be pretty steep.
I spent the better part of a month experimenting with WPF and writing a mock-up of our current product in it without developing an intuition for its databinding model or even figuring out how Microsoft means for it to be used. It took me much less time to grasp the basics of ASP.NET MVC.
[Our application displays/depends on a lot of real time data, and I used the Windows Presentation Foundation book by Nathan. Perhaps another book would have been more appropriate.]
