KDE 3.5 Kontact vs. "Proko2"

[Robert Szentmihalyi]

Hi,

could somebody please tell me the differences between the version of Kontact 
that comes with KDE 3.5 and "Proko2", which seems to be for KDE 3.4?
The KDE 3.5 version of Kontact works nicely so far with Kolab2, but seems to 
be older, AFAICT.
What are people using in production environments?

Thanks,
 Robert