|For me it was worth the upgrade. I had PS2K's on my cars and was really excited to get my hands on the elite. It offers a lot more flexibility and I really wanted to learn the new software.
The main reasons that I switched where:
additional safety features during tuning and post tune
More flex fuel features
All of that being said the Elite still has a lot of issues to get worked out. The pro plugin unit has been around forever and is mostly bug free. The Elite series are relatively new and there are still some fairly significant issues with the software / firmware IMO.
To get traction to work properly I had to do this:[ http://www.twinturbo.net/nissan/300zx/forums/general/view/2611961/Traction-Control-Hacking-the-Haltech-Elite-2500.html ]
So it really just depends on what you are wanting to do with Z and what features you are wanting to use. The Elite will take more tinkering to get ironed out than the PNP.