Glad you like it :)
Multisub-materials inside multisub-materials? Why would you want to do that? I'm a bit surprised that the script does not convert those but I'm not sure if this would have an effect anyways (in the rendering). Which sub-sub-material does the renderer choose if you have one sub in another?
Ok, I'll have a look at it, but I'm still curios ;)
And yes, this is the right place for posting bugs :)