Most common issue I found was that the pictures need to be resized for the size that you intend to print out before you gave the image to a lab.
10x15 cm printed at 300 dpi, even back 4 years ago, from a 6mp camera at full whack was too much information for that 6x4 inch print, hence some information had to be dropped.
Ironically printing grew significantly when they developed the process of translating a digital format from an analogue image, now the initial image has to be translated into the digital image format that was developed from the analogue format. so there has been a step added into the process, which created a range of perceived changes.
There is also some argument that the technology to create the image and represent it on the screen is significantly different to that used to represent it on a print.
But the core problem is that digital images are essentially linear, whilst film was randomly arranged, hence the images from the two sources will be different (despite the printing process being linear). Fuji have gone to great lengths to attempt to replicate this randomness at point of source, and it is just noticeable. See a comparison shots of the Nikon D100 and the Fuji S2 Pro pictures, where the image quality from the FUJI eclipses the nikon, for fundamentally the same camera.
This is why the inkjet printers actually produce a more aesthetically pleasing print than the Laser printers, because the inks have an opportunity to mix if even only mildly before drying.
Using a lab that has a fuji frontier digital printer is a good starting point on their crystal archive paper.
I did notice differences between Various Labs using the same hardware, which I can only draw to change of Chemistry.
There is also the issue of sensor sizes relative to the depth field in the print, with smaller sensors creating less image depth in terms of focus separation than larger sensors for any given combination of shutter speed and aperture for the same lit picture. My 5D compared to my Fuji E900 were completely different. and I dont think that this is just software.
Also note that the Lab technicians take it upon themselves to mildly tweak the image to the perceived best point. This may or may not help!
So in short resize and export your files to be printed out specific to the size of the print. Dont believe me - Print out a 10x15 inch and 6x4 from the same file and see if you notice the difference.
Where we stand with the New Nikon D800 and its stupidly large files I dont know!
there is then the fact that