I'm interested to understand the interpretation of gravity as a result of exchange of force particles (ie gravitons) vs General Relativity-based warping of space-time. Related to this is while a constraint to speed of cause and effect of c would apply to the graviton-based concept, why should this limit apply to space-time warping ? Re this latter point, I understand that while gravitational waves have been postulated there is yet no evidence of them (that in fact recent 2014 findings appear now to have been caused by interstellar dust). So I think my question can be distilled down to how can the theories of gravity as a particle-based force vs a space-time warp be reconciled, and what are the key implications of this ?
There is no tension between the two viewpoints. In fact, the situation isn't much different from electromagnetism. The analogy is photon $\leftrightarrow$ graviton and electromagnetic field $\leftrightarrow$ metric tensor.
Both of these theories, EM or GR, are field theories, and exhibit the phenomena of radiation. Gravity waves have not been detected yet but they surely exist :) In fact, they may be found very soon with Advanced LIGO coming online.
In a quantum theory, the excitations of the field are quantized, and this has been tested well in the EM theory but of course not at all in the GR theory. Now the full quantum theory of gravity is not known, and it has been the subject of intense research for many decades, but it surely possess something that "looks" like a graviton, the quanta associated with gravitational radiation.
There is huge tension between the viewpoints.
The current 'Firewall' debate - that QM predicts a huge amount of physics happening at the horizon where GR says that nothing at all should be happening is an example of the problems being faced in this area.