These are not exactly new "problems". Stu Maschwitz describes the limiting of values (that is cutting off blacks and whites) in his [i]DV Rebel[/i], and for DV, hence the name. I didn't understand why, it has to do with broadcast safety or what have you.The "fix" is quite simple: In your NLE (not limited to Premiere or FCP) open the luma waveform monitor. This should have a y-axis from 0 to 100. Lower the highlights until they all are crumbled under the "100"-line (some of them will go to 110 or so) and you'll get better defined whites, raise the shadows to "0", but not higher or you will get fog. Do all this with 32-bit floating point precision.
[color=#ff0000]Premiere[/color] shows you the quality of any filter as an icon right to the filter's name in the list, it is something like a folder with "32" in the middle. The [i]fast color corrector[/i] i.e. has it. Never use just one effect without the 32bit-icon!
[color=#ff0000]FCP7[/color] does [i]not[/i] show you if a filter uses 8-bit or 32-bit. There is this [url="http://documentation.apple.com/en/finalcutpro/usermanual/index.html#chapter=65%26section=2%26tasks=true"]list[/url], however, and there you see the little ¹ that indicates 32-bit-filters, the Color-Correctors are among them. As you can see, there are also many, many effects without 32-bit rendering. Don't use them. Let these things be done by Motion (where you change the bit depths in the projects properties, as in After Effects).
In [color=#ff0000]FCP X[/color] grading is not only completely done with highest precision, it is also no longer an effect, but just the always available [i]info[/i] of the clip - just never, never, never use the secret analyzing, auto-balancing and autocorrecting method FCP X offers you when you import media!
I tried the different settings of 5D2RGB, I tried ordinary Quicktime (did you know, that there is no gammashift in Quicktime anymore since Lion?), I tried .mov (7D) and .mts (GH2) as originals in Premiere, and I didn't find any permanent damage to the footage with any of the methods - as long as you do the contrast balancing described above manually and don't just hit [i]auto balance[/i].
5D2RGB is useful though for FCP X, because you may not have Cinema Tools, that allowed you to flag a clip with a different frame rate (within Premiere you right-click >[i]interpret footage[/i] and change the frame rate). During transcoding 5D2RGB can change 60p to 23,98p or whatever
.EDIT: My friend says, if you work for television, you are not to twiddle with the settings. Broadcast safe values were there for a reason.