For scrolling, it would be tricky since the rows sizes can be dynamic now. They would have to be manually calculated. It would be possible, but I'm not sure it would really be worth the code since so few people would use it. On a side note, moving through the grid with the arrow keys is a repeater now, so you can hold the arrow keys? I know that's no where near the same. :/
An idea would be to map the Page Down and Page Up keys to the arrows, so the user can use what he might be used to, without much disruption (and feature requests :-).