Just downloaded and played an hour or so with the preview version. Initial impression I have got is a slight disappointment. A couple of things cause this:
1) The quality of the raw conversion is not on par with Capture One, LR and DxO. The converted image seems to have a lower resolution.
Hi Cem,
Yes, I concur with that observation (comparing to Capture One Pro, RawTherapee, and Lightroom). I also ran a quick test on a very critical test chart frame I had shot some time ago, as the first image I processed with On1 Raw. I had tested other Raw converters with the same image before, so I knew what to expect, what was possible. Given that it is the same Raw data frame, the only differences were due to the converter algorithms.
The main issue is that the demosaicing quality is significantly poorer (at this stage of development, so that could hopefully improve). There is an off chance that this is caused by my Camera model not being supported yet by the faster conversion engine, but I'd expect that besides speed differences, the actual Bayer CFA demosaicing algorithm is the same.
With a much lower quality (demosaicing) input, we can only try and catch up at a later stage of development, but with at least one arm tied to our back. The garbage in, garbage out (GIGO) principle still applies. On the plus side, judging from the strange artifacts, I do see that they are using a self-developed method of conversion, so there is probably knowledge available to change it as well.
2) On1 has been making big claims about the speed. Unfortunately, the program is quite sluggish. Even slower than LR on my PC. When I slide/shift the controls, things are delayed and choppy. Refreshing the image takes time. It seems as if the graphic processor isn't being used (I have an NVidia GTX 1060 card).
PS: The program has crashed twice during my brief testing and had to be restarted.
It may be a bit early to draw conclusions about that, but it doesn't sound encouraging. I must say that my experience with the new contender is limited so far (it only became available for download close to mid-night local time, and installation took its sweet time), but I didn't notice a hugely different/slower response once the system settled a bit (OS and application caching and whatever refreshes were going on in the background).
Now I know that this is a preview version and they need time to iron out the initial bugs. That is why I'm only slightly disappointed. 
Same with me.
But I am seriously worried about the IQ. If it doesn't improve, I won't be using the ON1 raw converter after all.
While it may still be useful
after another program did the Raw conversion to TIFF, or for OOC JPEGs, I also do not like the idea of only using it for postprocessing. I agree that Demosaicing quality needs to be significantly improved for it to become a viable alternative.
I'll reserve my final judgment of the program for when it matures during the coming months, but they'll need to fix the demosaicing, otherwise it won't become what it's supposed to be.
Cheers,
Bart
