John Udell has written an article on WS Alphabet Soup based on his discussions with John Schewuck, an architect on the Indigo team.  Here are the interesting points:

• Indigo may ship before Longhorn to enable people to provide developers with access to the functionality provided by the newer WS-* specs.  I know the message from the PDC was Whidbey < Indigo <= Longhorn, but I guess haven't really considered it will come before Longhorn (I thought this was what WSE was for since Indigo is a 'baked in' part of the .NET Framework).  Not that I'd complain if it came earlier.
• There are a lot of Web Service (WS-*) specifications, but this is a good thing because they are composable.  You only need to implement the specifications you need.  The alternative would be a single specification that tries to do everything.
• The WS-* specs are inventing a lot of what has been provided before in DCOM and CORBA.  As Don Box says, 'The entire motivation for defining SOAP was to get the industry out of the "you need my runtime to talk to me" business that DCOM and Java RMI so happily got us into in the 1990's.'
• The advantage of using SOAP as a message description format  is that it provides extensible SOAP headers ("an accordion-like construct").  Previous network communications protocols was their dependence on fixed-offset dependencies that broke if you had to extend or modify the packets.
• Microsoft is wise to spend time worrying about the usability of its APIs.  This was my initial reaction at the PDC - 'Wow, they have done a lot to make this really easy for developers'.
• The key to reducing the cognitive overload caused by the specifications is an easy programming model (this acknowledges the reality that not everyone gets as excited as John Bristowe about a new specification).  Indigo's use of attributes in the Service Model is a major plus here.  How awesome is it to be able to write code like this to add WS-Security (signing, encryption), WS-ReliableMessaging and WS-AtomicTransaction support:

[Service]
[Security(Disabled=false, 
 SecurityProfileName="MyDynamicProfile",        
 ClientAuthentication=UsageMode.Required,
 IntegritySupport=UsageMode.Required,
 ConfidentialitySupport=UsageMode.Required)]
[ContextPropagation(typeof(ITransaction)]
[Connection(DeliveryAssurances.Full)]
public class MySecureReliableTransactedService
{
    [ServiceMethod]
    [Authorization(Role="Clerk")] 
    public void CreditAccount(string acc, decimal amount)
    {
        …
    }
}

The Loosely Coupled blog also has more commentary on the interview with John.