I have all four, actually
I love mine and use them on every shoot. I bought the BOBW first to see what i thought, and then bought the other three as soon as i could.
yes, there are many doubles, but you run out of the things that you use often (for me, the neutrals in the BOBW), fast enough.
Now that I have the other three, i mostly use my BOBW on myself, to be honest, as i don't need it so much, because I have all the others :P

Definitely worth investing in, in my opinon.