SRS: is there a stable implementation for postfix yet?

I guess the "Why SRS really sucks" thread reminded me that its time for 
me to poke my head up once again and ask what the current state of SRS 
is for an MTA like postfix 2.x

So far there are only untested patches and nothing that can be used in a 
high volume production environment.

I've always thought that the lack of viable SRS functionality has been a 
major factor impeding the adaptation of SPF. Without it, SPF is just a 
half-solution.

-mark