<p>Ok, I asked a question earlier about Flex and ADO.NET Data Services but didn't get much response so I thought I'd rephrase.  Does anyone have any experience building Adobe Flex applications with a .NET back-end?  If so, what architecture did you use and what third-party tools if any did you employ.  I've read a little about doing Flex remoting with WebORB but it seems more complicated than it should be, are web services an adequate alternative?</p>

I've mainly used plain ASP.NET pages that return XML for situations that are mainly one-way (data from ASP.NET --> Flex/Flash) communication. The Flex side just uses a URLLoader to hit the ASP.NET page and loads the result as XML.
If the communication needs to be a little more two-sided (sending more than a couple parameters to ASP.NET lets say), I have used standard ASP.NET webservices.
I've never used WebOrb or Flex remoting because I've never really needed that type of interaction between the server and the SWF.
Hope that helps.