Well- after a few people downloading and trying out the program, heres some reviews and thoughts.
Anon: tried out Saturn for a while this afternoon. It is essentially a stripped-down version of VS.NET that just allows you do to ASP.NET. It has all the components from VS.NET and even has a form for downloading new components from Microsoft's online component gallery.
There are many additions that are improvements over VS.NET. There are more templates (reporting pages, logon pages, etc). There is also the ability to have templated code. Currently there is only a "Send Email Message" code template. It allows you to fill out all the information about email address and subject and it automaticly generates the VB or C# code for it. I assume they will create more "code builders" before the complete release.
It also has a built-in webserver for serving the pages it creates, and can integrate with IIS, also. I have not found WebDAV support for connecting to remote servers. Overall, it's a nice looking product and if it will truely be released for free, it may make people wish thay had not shelled out the money for VS.NET just to do ASP.NET.
Thunder hood: Downloaded and tested the beta program from the Saturn site - it's very cool indeed. The UI is a mix of Office XP and Visual Studio.NET (more the latter than the former), and it has a very cool bag of tricks to make ASP.NET developer's lives easier. It uses VBScript and C# interchangeably, and has pretty incredible XML support.
A nice positive review of microsoft's latest program - and thanks guys for sending those in.