I recently bought a new camera and as soon as I had a good sunny day, photographed an IT8 target and made a custom camera icc profile with Profile Prism suitable for raw images.
I previously had used the Adobe RGB setting in QU raw preferences  and I seemed to be getting good results.
However, once I started using the camera custom profile, significant differences could be seen in the resulting colour accuracy.
I've attached 2 annotated images side by side to show the difference in this particular case.
You'll have to trust me when I say the custom profile image is very close to the real rose, a case of true-to-life colour.  
Of course not every colour will exhibit such a difference but this shows the advantage of using QU for raw processing, one of very few programs that can utilise custom ICC camera profiles.

Terry

Hi Mack,
Send me a personal message on this forum with you e-mail address and I will send you a pdf file of the information Mike has sent to me quite recently.
You could of course contact Mike at ddi support and he'll do the same.
Great care is required in photographing the IT8 target (that came with PP) and there is a bit of technique in converting the raw file for PP to use.
Terry

Hi Mel,
Not sure really, there's a lot of text!
If you have profile Prism, much is contained in the Help for actually taking the photo of the IT8 target and updated information can be obtained direct from Mike.
If you don't have PP, then you would need to do this anyway before sending a raw image to him for making the profile.
One thing that is not so easily found are the instructions for processing an IT8 image in Qimage Ultimate for your own use use in PP so I've posted them below as there is not too much text.

You first need to create a place-holder profile and put that in your Qimage application data folder under the "profiles" sub-folder. The name has to match the EXIF model for the camera.
For example, take a copy adobe.icm out of the application folder and paste it into the "profiles" sub-folder and rename it, for example, to "EOS 600D.icm". ( = your camera Exif name)
You can start with any profile because the profile itself doesn't matter.  You just want it to recognize that the camera has a custom profile.
Add the CR2 to the queue. Your camera profile name, eg.  EOS 600D.icm, should show as the profile in the queue.
Then right click in the queue, select "Convert Images" and select "TIFF" (or "BMP") as the image format. Do NOT tick perform a profile to profile conversion".
The created TIFF (or BMP) can be used in PP to create the raw image camera profile.
That created profile should then be used to *replace* the place-holder profile in your "profiles" sub-folder.
About white balance: Mike said it is ok. to WB in the refine screen: "I usually click on the third or fourth brightest patch on the gray scale to WB raw photos."
About image exposure: "try to meter for the target itself so that the white squares (one on the gray scale and the batch near the top that are "close to" white) are near 240.
The PP settings are shown in the attached screen shot and most importantly note the the gamma matching 2.2 and the -2 saturation.

I suggest anyone who is likely to need this information should copy it and keep in a safe place.

Terry

Markus & others,
You will see I have modified my post above and highlighted the settings information about saturation and gamma.
Terry