At this time, most of you have probably heard about the Web Services Interoperability Toolkit for Java (a.k.a. Project Tango), which enables maximal interoperability between the upcoming Windows Communication Foundation on .NET and the Java world. If not, go see http://wsit.dev.java.net/ ASAP.
WSIT will be tightly integrated with the Glassfish Sun Application Server, which also features full FastInoset support. In fact, Glassfish will – based on the HTTP header content type – automatically switch between text+xml and application/fastinfoset.
Now, with the WCF integration that FIFI will deliver, you will be able to configure an Indigo client at deploy time (or even after) to use the by far more efficient FI encoding. And this (re)configuration will only take a change in a single line in the .config file of that client (assuming that you are using a CustomBinding in the first place ;-)).
So, at the end of the day, you can start you deployment of SOAP and RESTful Web Services with angle brackets and as soon as you need a more efficient encoding, you switch to FI by simply setting the right config parameter in the WCF client. Can it be less painful?