yes it is the solid white plastic case instead of the old style clear case with white paint inside. the hinge is now white instead of silver, and the plastic surround keyboard and plam rest area is now a different texture (slightly rougher).
as for performance:
faster cd burner (24x instead of 16x)
G3 900 vs 800 - xbench went from 50.x to 59.x (128MB in Apple store base config for 12")
same video card
802.11b only
USB 1.1 and Firewire (400) only
conclusion:
Nice little speed bump, though the faster cd burner is the most noticeable change performance wise.