1 minor correction on comparisons...
Text is
not converted to 0 if both sides of the comparison are text. I've been using text comparisons against sub-class name to derive Market window menu selections for a while now.
Some of this stuff was experimented with and dicussed in
this thread 
I suspect the cat opperator was added shortly after that discussion and passed on to us in the semi-recent UIBuilder update. I did discuss this with one of Bobble's colleges around that time.