The downside is that backward compatibility has gone out of the window. There is sufficient compatibility that converting old code should not be too difficult, but errors can easily creep in. As a language it is hugely improved, although a little more demanding for novices. For web development this is a great improvement. Instead of VB Script, VB is available for web apps, running on the server for cross-browser compatibility.
Web services use the XML SOAP protocol to handle remote object invocation.
Microsoft has yet to announce a price for Visual Studio .Net. Verdict Visual Studio .Net is a major advance for Windows developers. This enables you to compare product performances directly knowing that all the other factors have remained constant.