What I can say after the first 24 hours in Open Mode: In normal day use I didn't feel any difference to my other N9 in normal mode.

All accounts are working (Nokia, Facebook, Twitter, Skype), Store is working, Maps and Drive is working. No password re-enter needed after reboot. What I didn't try though is lock code.

Only differences are big scary warning and devel-su; develsh grants me everything