Working with the NI 5785 our team had a hard time understanding how to use TClk without all of the extra (e.g. streaming) code that comes with the example.
Through support we were eventually put in touch with R&D and they told us how to initiate TClk by setting some of the FPGA controls. This was helpful but not intuitive.
TClk helps support beamforming applications shown in the NI Marketing but without this usability it is very difficult (impossible) to develop applications promised.
TClk also has other lower level features such as the delay correction. No info is posted on this either but it is a property we can read.