Sharper Images by Technique and Shot Discipline
Even at 24 megapixels, let alone 36 megapixels, peak sharpness is not just optical: high resolution digital demands consistent shot discipline.
Soon enough there will be a 50-megapixel Canon DSLR, with Nikon and Sony to follow presumably. While it’s not realistic to think that actual recorded detail will increase as much as the numbers imply (36 vs 24 is already modest), it is nonetheless realistic that under ideal conditions there will be more detail—with excellent technique.
Two areas in particular in Making Sharp Images address these topics:
How To Get Peak Sharpness With Perfect Focus
How To Banish Blur Whether Handheld or Tripod
There are many other factors, but specific optical behaviors like focus shift must also be understood in detail for any particular lens used: Focus Shift (Case Studies).