Looks like some serious color issues early this year...
Luminous Landscape Forum > HP Z3100 Problems with Colour Gamut
The internet is great for finding out stuff the sales guys won't tell you.
Most of those posts are from the Febuary time frame. Looks like there was some firmware updates that may have taken care of the issue.
Printing Insights #46 has a good log of issues.
What is disturbing is the feel from all the posts that HP is not recognizing the issue (or at least not being simpathetic to their costomers that just shelled out $4k for their product and now are pretty pissed) Finally found that HP had an official response.
Another thing I've been finding is that a lot of the people posting about their experience with the Z3100 have a 4000 as well, makes me think my 4000 is still well loved and deserves more attention.