Alright, let me supplement:
1) SB 600 is less powerful if compared with Di622...the guide number tells it directly.
2) SB 600 has lots of function for you to play with, for eg FV Lock, aperture etc etc; while Di622 is very straight to the point, only TTL mode and custom power level...easy to use and user friendly.
3) SB 600 has a built in LCD for you to tune, view settings etc...Di622 no LCD, just buttons and LED indicator..
4) SB 600 supports RF wireless trigger (like Phottix Tetra) but does not have built in optical slave. Di622 has built in Optical slave but does not support RF wireless trigger...
5) recycling time of SB 600 is slightly faster at ~3.5 sec while Di622 is ~4...(fully charged Ni-Mh batt)
The above are all that i can think of currently...i might left out some...others pls supplement...
agreed with u.. especially on item 2, 4 and 5.. tu paling penting.. hehe.