Ok, here's the new deal...
there are two subpatches for testing, one is light with a relative big window partition (1024) and a short Impulse Response (2 secs).
The other is quite heavy, it's an 8 sec long IR with a window size of 512! This one takes just a bit over 50% of my CPU power, and I'm on a last generation macbook pro (2.6Ghz processor)... but I need to increase the Delay (msec) from 5 to 10 in the audio settings, otherwise I get terrible clicks!
William Brent's convolve is ridiculously much more efficient, the same parameters take about 14% of my CPU power and I can use a delay of 5 ms in the audio settings.
But anyway, this is useful for teaching and apps that implement a light convolution reverb (short IR/not too short window) need pure vanilla (libpd/camomille and stuff)
Cheers!