I have noticed the Progressive Render is the default render, but I am rarely seeing it used in any of the examples by Chaos Group. Is the Progressive Render used for only certain occasions?
Some people like it, some people don’t find much use for it. Personally, I don’t use it. It’s not faster, and might be slower, however you can set a time limit on it. Why it is default? I am not sure. I know Vlad likes it and he has a little influence 
It’s great for test rendering, especially when testing compositions and lighting! Because it’s progressive you get an instant idea of what general things are doing and if you want to let it refine further, to make out a bit more detail, then you can! Rather than setting up draft quality settings, then stopping it to put in slightly higher quality settings and so on. I still use adaptive for final renders however i know Mr Guthrie has started using progressive all the way!
Progressive sampler is fantastic because you get very quickly a workable render to set and adjust lighting and also roughly adjust materials. On my main workstation, dual xeon, it works great and I even did some final renders with it.
But when doing distributed rendering it’s another story : it’s slower because nodes CPUs usage never reaches 100%. Also if a node drops out for any reason it seems the rendering hangs there forever. Not sure if this is still the case with the latest version of V-Ray though.
So for the moment, Progressive for test renders and Adaptive for finals. But I’m very close to switching to Progressive because on tight deadlines, being able to stop the render any time knowing that I’ll have a complete image, albeit noisy, can be a lifesaver.
for DR though we have to go back to bucket rendering, just cant get progressive working well with DR at all 
works ace in DR mode here Peter…unsure why its not working for you?
I am getting clean Full HD frames in 13 minutes in my interior renders here over the DR
EDIT:
actually i never used progressive without DR
let me try runnign it on one machine a nd compare times
might work ok with small scenes, but with the scene i am working on the slaves never use full cpu utilisation when rendering… but they work great on bucket mode. I have experimented with a higher ray bundle size to no avail
yes its miles faster using DR than single machine so it must be working i guess
99 percent on all participating machines.
Regular interior scene, equipped kitchen and living room, lots of glossies etc…
No plugins used though…perhaps its caused by some 3rd party plugins such as Forest?
I also don’t have full cpu itilisation when using DBR and progressive image sampler.
Using Max2016 and Vray 3.40.02
Buckets are fine - all machines run at 100% but cant get more than around 30 - 50% when using progressive dbr to other machines.
Shame - as I really like it as an image sampler - very handy to just let a render run for an hour to see what you get…no unrendered buckets after lunch !
Same here unfortunately. Setting the ray bundle size higher doesn’t help.