I'll bet the community has some good input on issues to watch out for, but in principle this 2.x-to-6.0 cross-platform upgrade is completely doable, with the appropriate compatibility conversion kits. That's one of the great things about LabVIEW.
The NI Web site has a nice Upgrade Advisor (http://www.ni.com/upgrade) that can help identify the elements you would need, including the compatibility kit info. Ultimately, you'd want to contact a sales engineer (http://www.ni.com/contact.htm) to get all the details.
The general things you would not be able to take along with this upgrade are Macintosh-specific VIs (there are few) and any VIs with Macintosh-based C code interface nodes (CINs) that you programmed yourself. If you're not familiar with CINs, then you're prob
ably pretty safe.
Regards,
John Lum
National Instruments