Sysprep Vista - do I have to?

I am confused about sysprep and what it actually does. Was hoping to
clear up this issue. I thought one thing sysprep did was prepare a
machine for an image by doing something with the SIDS. Here's what I
did with XP.

Create my image for my network domain. I do not use and unattended
files. All I do is create the image by adding the machine to our
domain, loading all software, copying the default profile to "default
user". I then remove this computer from our domain, image using ghost
(very basic). We then dump the image back down to like machines and
add them all back on our domain. No isues. We have a School Site
License for Microsoft.

Now we are moving to Vista and have a KMS licensing server. From what
I have read and been told you must run sysprep before imaging. So far
this has been a headache. The first image went ok but since we
haven't explored any unattended files the sysprep seemed to do more
then what we needed and we had to reinstall some drivers etc. The
second time I ran sysprep I got a fatal error and had to start over.
Since all our machines are identical why can't I just do the same
steps as with XP. Shouldn't removing the pc from our domain right
before imaging resolve any SID issues with the KMS Server? Isn't that
what sysprep does? If I remove this imaging computer from our domain,
ghost it to create the base image, dump it back down to 20 other
computers and add them back on our domain individually shouldn't they
all license fine with our KMS Server (aren't unique SIDS created at
that time of adding back on our domain?) I'm trying to avoid sysprep
since it seems to add a layer of trouble to our image process.

Thanks for any info on this. I read different articles but I seem to
still be missing the whole picture of sysprep. Especially when we
don't need to do anything special with answer files.

Dawn