I have a background of both commercial litho and packaging with both Preps and Signa. Signa is hands down the best commercial litho layout/imposition software on the market. My opinion diverges when it comes to packaging. I have recently evaluated Prinect/Signa vs. Esko's Suite with Plato + ArtiosCAD. These appear to me to be the only two really serious players in the packaging market right now. One is very well established here and the other wants a big slice of it.
Heidelberg's CAD program and packaging layout is new - I mean brand new. The previous versions (4.5 and earlier) of Signa + packaging felt like an add-on that was reactionary rather than visionary. The new version is much more robust.
If you love Signa as you already have it and if you are primarily commercial litho with packaging on the side I suggest you stick with Signa. If you are primarily packaging or plan on becoming primarily packaging I suggest that you give Esko's Plato a serious evaluation. Esko has something like two decades of experience and a massive amount of market share (>70% if memory serves) in packaging compared with Heidelberg's brand-new CAD and relatively new packaging function in Signa.
The source of the difference:
CFF2 files are a pain - they contain the die-line and really nothing more. Intelligent meta data for bleeds, margins, smart mark areas, glue flap detection, varnish/ink free area detection, etc. are not carried over. It is my opinion that this is why Heidelberg has jumped (more realistically stuck their small toe) into the CAD arena - to create a proprietary fusion between CAD and imposition like Esko has been doing for a long while with Plato and ArtiosCAD. This allows the import of intelligent meta data and allows automation and intelligence to bridge this step - eventually leading to the end of the need of imposition personnel.
I feel that CAD is an area that is not and will not be a focus for Heidelberg as they are likely only taking it on as a necessary evil to sell other higher margin products (presses, folders, gluers, cutters, CtP equipment, and consumables). On the other hand Esko is a software company that also sells flexographic plate setters and CAD tables - software is their primary focus. It is going to be very interesting to see what Heidelberg does and how much they are willing to commit to getting this done and done right. Packaging is a growth market that they need but their revenue models are not built on developing and selling software. I am beginning to wonder if they are trying to do too many things at the same time.