"Film-era" lenses often don't perform well on digital sensors, even if they perform well on film. Most digital capture is much more sensitive than film is to chromatic aberration. This can cause lack of sharpness, especially in the corners, that wouldn't be particularly bothersome in a film capture.
The reason? Film is sensitive to all three capture colours throughout its area. In other words, a given spot of film can capture all colours in a vertical stack. Most digital sensors have the three different colour-sensitive pixels adjacent to one another, not stacked. It works very well for most purposes, but it magnifies chromatic aberration. (I understand there are a few sensors that are designed differently and aren't sensitive to this, but they are relatively uncommon.)
You can see the consequences of this in the rise of ED/LD glass in what were, in the film days, relatively simply designs. You can even find ED glass in 50mm full-frame lenses. And to be sure, this has some benefits for film photographers - the aberrations were there when shooting film, too; the effect was just smaller.
There was an interesting thread on Photrio recently about the opposite effect. Digital is, in effect, much less subject to issues from distortion than film is. It can be corrected in post-production in digital photography, but in straight film photography (without a hybrid workflow), there is no way to remove distortion. Some systems are now seeing very sharp, low-chromatic-aberration lenses where distortion is sacrificed to keep prices, size and construction reasonable, because on digital, it's not a problem. These lenses may not perform terribly well on film, though.