This subject was covered extensively on Edmunds.com for months. The new Si's will burn what appears to be alot of oil for the first 3 or 4 K miles, then settle down to about 1/2 quart every 3 K miles.
The iVTEC system is all different from the previous version of vtec. The crossover point is like 3.3K rpms. It's on almost all the time without driving too aggressively. That's why the gas mileage sucks compared to the 5th generation. Most guys were getting AT BEST 30 mpg per tank on daily, mostly highway driving, where on my eg hb I would get 37 mpg average even after almost 200k miles.