The CMYK values from the pantone colour bridge tend to get close to the dirty CMYK swatch on the right side of the book, but not close to the left side solid colour. I've tried using the RGB values shown in the colour bridge where the software lets me and the result is often better in the blue shades, but not so much in the rich greens and reds.
I know other rips can hit the pantones a lot better than the freebies with the same ink and printer. Why not these?
A more sophisticated RIP will usually include LAB lookup tables for Pantone and other spot colour libraries. These tables allow the RIP to ignore the limitations of the CMYK source/input profile (or RGB source profile) and simply attempt to hit the LAB colour as close at the printer's output profile allows.
Ideally you should always use the spot colour name from within your design software and not the 'CMYK equivalent' that you refer to on the RH side of your Pantone Colour Bridge. Using the CMYK will always be bound by the source profile's typically smaller (and dirtier) gamut.
Unfortunately the RIPs provided for free, along with many of the other average RIP offerings do not have this level of colour management built-in, and therefore are unable to get the most out of the printer and ink combination.
I'm really interested in what other users have experienced.