SAML simplesign useful in practice?

Over in the XRI TC there is a design item to be finished regarding signing 
of XRD documents, and the perhaps predictable discussion of whether 
specifying XML DSIG would be a barrier to adoption, hence whether to 
specify something similar to the SAML simplesign method.  In fact the 
existence of SAML simplesign is held up as evidence that DSIG is a 
problem, and of course that is indeed the justification for simplesign.  I 
think the most compelling part of the argument was that implementations of 
DSIG for some popular scripting languages (eg PHP) were lacking, creating 
the adoption problem.

So the questions being asked of the SAML community are (a) whether 
simplesign has been implemented and deployed and has enabled more adoption 
as intended; and (b) whether, at this late date, acceptable XML DSIG 
implementations now exist for all those languages such that signing via 
DSIG isn't a problem any more (which might explain why the simplesign doc 
is still at CD stage perhaps).

Does anyone here have any observations or opinions on this?

  - RL "Bob"