I noticed the new voices quickly. On the plus side, Dana Delany returns as Lois and Tim Daly returns to voicing Superman; he hasn't played him since S:TAS ended in 1998.
The "regular" voice actors for Brainiac and Luthor were either tied up voicing for JLU while this was being made, or, the producers of this movie maybe wanted to save time/money by recasting them. It seems very obvious that the only reason this DTV is being made and released at all is to capitilize on the SUPERMAN RETURNS movie in June. WB is having a whole slew of Superman related DVD's coming out this summer; BRAINIAC ATTACKS is only one of them. Therefore, the production was likely on a strict timetable.
It doesn't look bad, some of the action sequences look well animated. I'll naturally give this one a rental.