The media rating is based solely on the consistency of the track or layers. The drive itself has to make sure what it is trying to write is written, that's why it reads it as it writes it and compares it to the original file on the hard drive. Burners have write error detection, and you can enable a second check with most of them.
Higher quality discs can be burned faster without errors because there are fewer inconsistencies. However, the rating is only a guaranteed rating which was put in place by the group overseeing the standards for DVDs (DVD Consortium, now the DVD Forum). A 4X DVD-R can in fact be written at 20X speed, it's just very likely to produce errors and not be a readable disc (who hasn't made a coaster trying to burn?).
Higher quality discs were never made because that perfect of a disc is rare to create and was never really needed due to few readers being able to burn that perfectly, not to mention many people write at slower speeds for perfection and better quality anyway.
A 24X burner may pave the way to better quality DVD discs, but due to the scratching problem that DVDs have, and due to Blu-Ray already being larger capacity and more resistant to scratching, it is likely that this technology will simply find its way over into the Blu-Ray market. It may not be heralded as a GREAT invention, but it is still a WORTHWHILE invention. It is similar to ramping up from a 5400rpm hard drive to a 7200rpm hard drive and being able to obtain the same longevity/heat output.