Let's face it a +1 bonus to damage is boring. Maybe not at first but improving things from +1 to +2 isn't very exciting either. How about beefing things up? A simpel little change instead of a +1 sword being +1 to hit and damage it is instead +1d6 to damage. A +2 sword is +2d6 to damage.
Sure it's just dice rolling but it's more dice, using that magic sword at the table looks different, it even feel different.
With more dice on hand magic swords become more significant and all of a sudden fighters gain a lot of ground compared to magic-users. Sure beating tough monsters becomes more likely.... since when is that a bad thing?
One also gains a mechanical method to add special effects to magic swords. With each 6 rolled on the magical damage dice something special may happen, depending on the weapon of course. On some weapons something bad happens whenever a 1 comes up; possibly an ego battle if you have annoying character stealing intelligent swords or a crackling backfire of magical energy... something that makes swigging the magic sword iffy even when successfully deployed.
Just a notion for now. I'm likely to go with more from here but I felt like sharing.