I also use a HP 455CA. It is 300dpi. The printing is a bit slow, but with the auto cutter you can spool a dozen drawings and go for lunch. It definitely seems to be a Windows item, modified for a MAC. I use it for architectural drawings, and have not tried full color renderings, but coloring elevations is fine, given the limited color choices in Vectorworks
Software quirks are always a bit of a problem between VW, where they won't discuss printer driver problems and HP that doesn't talk MAC. There can be good exceptions though. one minor problem is that the VectorWorks drawing size does not quite line up with the printer, so there is a lot of fine tuning to get the boarders and title blocks on the edge.