What kind of performance are you getting from the RadeonDDR64 on Tribes 2? On an overclocked Geforce GTS 32mb card running on a Duron 900 I'm only getting 20-45ish frames. On average the framerate isn't acceptable as 25 frames isn't too acceptable to me and I've tweaked the system quite a bit. This is at 1024 x 768 with some options on max but most set around 75% of max, no sky, no - low shadows.
Regarding the Kyro II and Tribes 2, here is a statement from PowerVR taken from Planettribes.com:
Microsoft's DirectX 8.1 is aiming to fix issues with the Kyro 2. Under the beta of DX8.1, my Kyro 2 testbed's FPS improved by 5-10 fps. Also, a PowerVR representative informed me that the future Kyro 2 drivers are going to be designed with Tribes 2 in mind. Just though I'd share that info.
If someone out there is running Tribes 2 on their Kyro II at 1024x768 or higher (I doubt higher..) at 35 frames average or so with almost max settings, please give your system specs and describe performance. Tribes 2 is an awesome game but it's really hindered by it's insane requirements as the minimum specs required to play T2 on the box is something to laugh at.