the objects rfft~ and rifft~ are dropping the Nyquist bin, and the imaginary part of rfft~ is inverted, but it corresponds to rifft~. for music it is ok, for scientific use we should fix this bug.
i'd love to change this. this is the reason, why i had to add a function to inverse the imaginary part when using the fftw library. the thing is, it would change the behaviour and people might rely on the old behaviour. i second you and would prefer to change the behaviour ... at least in devel, but having two different behaviours would be even worse than having a wrong behaviour of both branches...
this is definitely something to be discussed in the irc developer meeting that will hopefully take place, soon ...
cheers ... tim