Well, I found this quite interesting. I just got my copy of GPO yesterday in the mail and installed it today. I'm running a Macbook Pro with Leopard. The installer worked just fine, the NI service center updated everything.

To make a long story short, GPO installs and works in Leopard. I was under the impression that it was not even supposed to install. The only issues so far have been the NI Service Center not validating GPO, and it not being able to find the sample files until I clicked the "Resolve Automatically" button, upon which GPO KP2 found the samples and loaded as normal.

I'm pleasantly surprised to say the least.