your mileage may vary, especially as a newer version of the os2008 is now out but i found that if i reinstated a backup from os2007 on os2008 the os was quite unstable. reflashing and starting from scratch and the new os is pretty solid (still the odd app crash or lockup). I belive others here have also reported problems if using a backup.

someone elso may be able to shed more light on weather a specific part of a restore causes an issue or if its just pot luck how smooth it goes.