I'm new to the BB. I own a "mystic gold metallic" ES330, and am also experiencing chipping problems, and also only on the hood. A friend whose wife drives a white ES330, has a similar problem. I have ~5000 miles on the car. I never had this problem with a "platinium-gold" Nissan I owned (in 65000+ miles), so am uncertain about the comments made regarding some paint colors being more susceptible to chipping.
Although water beads up nicely still, I will wax the car to see if it alleviates the problem. Even so, I feel this is a manufacturing flaw or weakness that Lexus should address and repair. In the meantime, I have bought some touchpaint to protect the chipped areas.
Having said that, the car is by far the best I have ever owned. It appears to be aging nicely. Its performance at 5000 is better than when brand new, and the gas mileage appears to be improving. I have no complaints about the dealer's service.
Just thought I would add my experience...