The chosen colors are represented properly in the render. I would say it's more a matter of not properly accounting for the effects of lighting, atmosphere, etc. The difference between TG 0.9 and TG2 in this regard probably comes down to 3 factors - Global Illumination (not present in TG 0.9 at all), different atmosphere model (an improvement over TG 0.9), and a different tone mapping function (so-called "soft clip", although I believe it is still similar to TG 0.9).
In any case I would not expect drastic differences, nor do I think it is really that much different from TG 0.9. One other factor that may actually play a greater effect than anything is that the *method* of choosing colors is completely different now. The full color palette, as opposed to the little sliders, changes how you will pick colors a lot. The swatches are also larger now I think. Not to mention that it doesn't show a range of exposures as it did in TG 0.9. Enough differences anyway that it could be having a notable effect.
Actually, one thing that just occurred to me is that TG 0.9 had a way to adjust both the render gamma and the GUI gamma. If you adjusted the GUI gamma I believe it affected the surface color previews accordingly. I'm not sure TG2's render gamma has the same effect, or even whether it should, but that might be an additional factor as I know a lot of people turn down the gamma to get a more saturated look.
That being said I do think colors render as they're "supposed to". I too have had trouble picking the exact right colors, but I think that is partly just because we have unrealistic expectations about real-world colors. In the specific case of sampling from a real image you will run into a lot of difficulty because of specific lighting, atmosphere, camera, white balance, and other factors. I don't recall it being all that easy to match colors in TG 0.9 either, nor do I think it is particularly effective in other similar applications.
Still I agree there's room for improvement, it's just that the current systems work well enough and give you all the power you should theoretically need. Anything more would really be a "helper" type of tool. Something to think about for the future...
- Oshyan