So that means that you get lower quality renders for texture baking if you aren't using FG.
In this question you should use Noise level not lower quality. It can NOT be compare QMC with Final Gathering because this first one produce no interpolated GI so quality is far better then Final Gathering. Noise is not big problem - if has good acceptable level for cleaning in post process.
Sure it can be used, but you wouldn't choose to use it for all of them, surely...
In attachment some my renders done in Path Tracing. Time renders under 20 min...impossible to achieve by Final Gathering.
Well, if you read about the various unbiased engines, they all talk about speed optimisations. Mathematically I'm sure it is possible, but you're right about the principle.
There is nothing to speed up. It is pure CPU/GPU calculation. Saying: we optimised speed render 20-40% in Path Tracing it is partly true because is nothing to speed up! It can be speed up by tricks: for example in first minutes Path Tracing Photons are interpolated by special part of code or noise is reduced more by new algorithm. The first trick allow user to see something in the first seconds/minutes of render. I think many unbiased engine renders has some trick for that because let's say true: Path Tracing is horrible slow. Without these trick it would be impossible to see something in first minutes!
If you want check how slow is Path Tracing download demo Octane and start one of the demo interior scene with PURE 5 bounce Path Tracing render (without Direct Light trick and OCC)
I have to say that I find this a little depressing. If you want to render with an unbiased algorithm, there are already quite a few render engines like Luxrender and Yafaray that already produce great results for free. The algorithms are all basically the same, so if your modeller is supported, with comprehensive materials and tonemapping options, technically there shouldn't be much difference between any of them. You could argue that with good PP, tonemapping isn't critically important either...
If we talk about free software: of course it`s true but is one problem: The power of render engine is strongly connected with possibilities of software 3D.
In Lightwave case: one of the best Instances system, one if not the best Nodes system, one of the best animation system, one of the best modelling system for architecture (Modeler + LWCAD). In Max3D the same situation.
If you are going to accept the long time (but often the benefit of simpler setup) for an unbiased render, and can get the software for free, what is the point of paying for something like Kray if you can't get similar quality much faster? You could also argue that with network rendering, potentially even the speed benefit of unbiased algorithms are negated..
I use Kray not because of "Kray"

but because of Lightwave.
Isn't biased rendering the whole focus of Kray - and Vray? You get great results, really quickly. If you tell me that for biased engines to get similar quality, you need similar (or longer) render time, it's quite a statement. In my humble opinion, the unique thing about Kray is its balance between quality, speed and (relative) simplicity. I think Kray is a fabulous piece of software, but your statements about unbiased techniques to me are shocking because they imply that there is no point in using an engine like Kray...
Is not time for Path Tracing yet. Next 5-10 years. Today king is Final Gathering.
Kray3 will have hybrid CPU/GPU (Is partly done in code). Some parts of render are done faster by CPU and is better to focus on hybrid then totally drown in GPU.
Let`s say true: 90-99% of renders done is by Final Gathering or QMC
I guess that remains to be seen
I haven't seen examples of typical scenes (interior or exterior) which are a direct comparison (including render time) between Kray 2.5 and Kray 3. I guess this is what we are all waiting for!
I could test it in K3 pre beta 3 because Final Gathering had bug with this (it did not work at all) Patience
I accept that for some scenes QMC can be faster, but personally I haven't seen many.
See attachments

Auditorium has
- almost 600 Instanced chairs
- 10 Physical Lights (Area Lights)
- 170 IES Lights
- around 300 Lumi Lights (halogens)
This scene I render much faster in QMC then Final Gathering