If you are talking about the 5.6x28mm Otis cleaning kit, I have one.
Its a great cleaning kit, comes with
1 ) a "bore snake" style cleaning rod/cord
2 ) some unique patches
3 ) P90/PS90 cleaning instructions
4 ) "General" firearms step by step cleaning poster(pistols, shotguns, rifles)
5 ) "Otis" cleaning solutions/oil
6 ) Brass Brushes and tools
7 ) Neat little carry case with FN logo
8 ) GREAT Video CD of how to clean just about every type of firearm out there. You select with gun you want to see and the video walks you through dissasembly, cleaning, and reassembly. If you want to know how to take down and clean a certain gun, its probably on this CD.
So to answer your question, is it worth it?
Only for the video CD, if you just want to clean you PS90 then no.
Its cheaper and easier to buy a bore snake and a cheaper cleaning kit.
I only bought the Otis kit because I wanted to have an "offical" FN cleaning kit. But I've never used it other than looking at the CD and poster.