[BioC] Standard error in summarization ExpressionSets

[Rodrigo Santamaría Vicente]

Hi there!,
After performing normalization-summarization with any of the available 
functions (rma, mas5, plier, etc.), I get an ExpressionSet class. It 
inherits from eSet class, but it seems to loss the se.exprs() method to 
get the standard errors for the summarized expression levels.
My question is: how could I get the standard errors from the 
ExpressionSet returned by rma, mas5 or any other method? if these 
methods do not return standard errors, why? are them unimportant? is 
there any method that computes them?

Thanks in advance!
Rodrigo