I noticed a big change between spider-man 1 and 2.
In the first movie, one of the problems that really irked me, as well as others, was that they recorded Tobey's lines on location; the practicalities of which resulted in a somewhat muffled sound when he spoke as the mask served as a filter. The mask also seemed a lot more 'solid' (for lack of a better word) and the movement of Tobey's jaw could not be seen as he spoke, giving spider-man a mute expression.
The second movie corrected this by dubbing Tobey's line, Spider-man's voice was now crisp and clear, there were also a few instances where we saw movement in spider-man's mask, implying speech.
These changes, although helpful, have yet to deter Raimi from removing Spider-Man's mask all together for the third act of each film. In his defense, I get it. You paid an actor for his talent, his face should be shown to create the illusion that it's Tobey behind the mask and not always a stuntman. I think in the first spider-man is was done with good reason and the mask stayed on for a fair portion of the time, although tattered, after the goblin bomb. The second and third movie make weaker attempts at justifying this.
As for his eyes, I know the comic takes liberties in actually showing the change of expressions through the mask, I'm not entirely sure this would translate well into the film version. That being said, it would not be entirely difficult to write in.
"Look MJ, I've found that my lenses create a glare when it's bright out but I can't have them tinted or I won't be able to see at night. I've created an iris mechanism that would adjust my lenses for day and night using a blah blah blah light sensor."
I mean, how does the flux capacitor actually work? 88mph explains nothing :P
There is a problem with them constantly unmasking Spider-Man. Perhaps animating the mask might help keep this from happening.