When I got my HP-CS I ordered a Crown Cap at the same time because it was only $12 extra, so what the hell.
Was it worth it? Good question, I don't really know, but I use mine all the time and it seems to work as advertised.
FWIW, get yourself the .5mm needle, .5mm nozzle and .5mm nozzle cap (check this with saltydog). This will turn your HP-CS from .35mm HP-CS to .5mm for wider coverage jobs for about $20.
You won't be sorry ordering the Iwata it's fantastic.
Cheers
Darren