Thanks very much for your post.
We are also considering it. However, we came across some issues.
Our application is already on ASP.NET 3.5. We were looking at 2 important issues which Visual WebGui does not have any workarounds which is kind of non-starter.
1. How to use the Site Map Provider for Menu.
2. APS.NET security integration. We have our own Security Module extension with CSLA to provide roles and role specific custom properties.
Both of these are not supported by Visual WebGui.
I would be most interested to know how you are tackling this in your app.
Thanks in advance
Kip