This is one of those utility modules that proves to be more useful than you'd think.
I've mounted mine at the edge of my modular's case so that I can easily access the controls rather than getting lost in the spaghetti of a complex patch and I use it for performance controls. Just a straight voltage through it and mult the output and I can sweep the cutoff accross my three filters ...all at once! Lovely!
I also use it for subtle control over modulation depths (often for vibrato). You can of course put audio signals through it as well to send a dry signal to several effects at once (again through a multiple - I have a multiple mounted right beside the dual attenuator as I often use them in tandem).
It's inexpensive, small, versatile and very useful.