Hi there,
I completely agree with what Fixx said.
To me preparing my work ready to print is vital for 2 specific main reasons (there are others too but they are mainly related to my workflow).
1. I want my artwork to be print-ready so that i have control or let's say legal certainty and using a bitmap to tone an image with Spotcolors is the usual way how prepress will handle it.
I do comic art and the reasons why this is important here has already been sufficiently explained earlier.
2. I have been working in a prepress department for quite a while and I do want them to have exactly what they want if need be and have them not necessarily do it themselves because the very least it will cause is a delay which of course might provoke other problems.
So yes, bitmap is absolutely necessary and other prepress related features such as a preview of color-separation and overprinting.