I am very happy with VSig too and I think that the comments Boklanoei made are unfair (regarding VSig). You just can't expect to have an effects processor which is that deep and demand the VSig to be easy and fun.
Of course, VSig can always benefit from an upgrade – what I find annoying is the inability to see what cable is connected where. The way it is now, by clicking on an outpout you see a whole module outlined and modules often contain dozens of inputs and outputs. I think it would be great to highlight the cable itself and maybe bring up a pop-up window of the name of the respective parameter.
Another thing which doesn't work that smooth is the zoom in and out controls – they are a bit awkard. When zoom in, I would prefer having the cursor change to a small hand (like in Adobe Reader for instance), instead of scrolling.