No, it's not. In fact, apart from AOS3.5/3.9 (and software that requires 3.5/3.9) there's hardly anything at all that requires Kickstart 3.1.
Good point..
For me, it's just because I've been running WB 3.1 for a while (I know you don't need KS 3.1 for WB 3.1, but they were sold together), so I'd like to own the kickstart. And I've considered 3.5 and 3.9... (But haven't decided yet, as 3.1 with "stuff" is pretty good)
So true, you don't need 3.1 unless you are planning on running 3.5/3.9 stuff really..
desi