One thing I hate
When you erase all the private data, you loose all the images in the speed dial tiles. It wasn't like that with Opera.
SpeedDial previews should not be cleared, that is a nasty bug. This will be fixed, but i dont know when. But i could see this was discussed by Vivaldi's CEO Jon von Tetzchner and other Devs in Bugtracker that the issue has a high priority and should be fixed early.
I hope this will be in next Beta.