I just recently installed Mavericks 10.9.1 over a Lion Installation on a spare partition to test compatibility of applications.
Reading through this discussion I thought I'd do some test myself on my Sandy-Bridge System with NVIDIA GTX 650Ti and compare those with the behaviour on 10.8.5 which I still use day to day.
I have not changed the AGPM-kext and I am still using MacPro3,1 as a system profile on both versions.
Luxmark 2.1 freezes clock rate on both systems to maximum level, FCPX works well on both system and VLC and Quicktime also play back without hiccups at lowest GPU clock for a H264 576x768 video.
The only difference I could detect so far is that 'Preview' freezes the GPU clock at its highest level on 10.9.1 when displaying JPG, while it does keep GPU clock at lowest level using 10.8.5. PDF-files are not causing this freeze.
SpeedStep on CPU works great on both (I am using Chimera 2.2.1 with "Generate P-States"=YES and "Generate C-States"=YES and a DSDT for my motherboard)
Please see details in the attached file.
I should mention that I am using the latest HWMonitor under 10.9.1 while under 10.8.5 I am using the version from Mulitbeast 5.5.5.
So my conclusion is that there are still issues with the OpenCL implementation (probably carried over from 10.8) and that modifying AGPM-kext has no effect at least for my GTX650Ti regardless of OS X version.
While I can live with the Luxmark issue, let's hope Apple fixes the issues with 'Preview' in 10.9.2.
[EDIT] Please see also my experience with AGPM under 10.8 here:
http://www.tonymacx86.com/general-hardware-discussion/75540-gtx-650-ti-thread-8.html#post539800