I haven't try OS2008 with my N800 but...

I was reading User's guide of N810 and found out that Clear device... feature will remove all your data from internal non-removable memory card from N810 and I think this means removable-internal card for N800 users. So be careful out there if your going to use N810-OS2008 in your N800 because this feature may remove all your data from internal memory card

I think this feature will work differently with official OS2008 release for N800 or I really hope so