My subjective findings, based on a necessarily limited number of samples and my own limited, non-professional experience, make me realize that Adobe has from day one met with no cooperation from Canon and Nikon regarding their raw formats. This impression is reinforced by reviewing old posts in this forum that show the most complaints about subtle and not-so-subtle disappointments with the rendering of raw files concern these two giant market leaders.
ACR eventually catches up and continually corrects deficiencies noted by users.
By contrast, those of us who use a variety of other camera brands, in my particular case Pentax DSLRs, find that ACR has always hit the optimal rendering of Pentax PEF and DNG files from day one or has come darned close to it. Thus, the new 2012 rendering and other ACR improvements have a much greater impact on Canon and Nikon image captures.
It would be interesting to hear comments on the experiences of users of other digital camera brands, other than Nikon and Canon.