33-34 is about right. 44 is the max for the load rating and would be absolutely incorrect. Handling would be terrible (not enough tire on the road) and the ride would be very stiff.
Just as a note...I have an 09 Hihy, now with 1200 miles on it.
Mine came from the dealer at 40psi. The door sticker does indicate 34 on mine. The max PSI on the tire sidewall (for maximum load) is 44 psi. Based on how low profile the tires are, and the rim width to tire size ratio, I was guessing that running at or near the max PSI would not have an adverse impact on the tire wear. The stock rims are perfectly sized for the stock tires. If rim width is off, or on tires that are less stiff and/or have taller sidewalls, changing inflation pressure can have dramatic results. Overinflating can cause the tires to 'balloon', resulting in the center of the tire wearing prematurely, and less tire on the ground (the edges of the tire being slightly removed from the road). Underinflation causes the opposite, with the sidewalls carrying more load, and the edges of the tires wearing faster (and the center not wearing as fast), and also potentially leading to sidewall failure.
I've done some tire pressure experimentation. Changing from 35-44 psi really doesn't have a significant impact on the handling of this vehicle; even at 33-35 psi, the low profile sidewalls ensure a rigid tire response. I've also chalked and marked the tires, to examine tire wear at different pressures. From what I've seen, the tread profile and wear patterns remain wholly unchanged going from 35 to 44 psi. To be clear: my testing suggests that there is NO CHANGE in contact pattern, and thus should be no change in tire wear. Also, at 44psi, the ride is still great.
I haven't had a chance to test fuel economy at different pressures yet. However, based on experience with previous vehicles, my review of the experiences of other hybrid owners, application of basic scientific principles and good clean common sense, higher pressure = lower rolling resistance = better mileage. So for now, I'm sticking at 44psi.
Oh--and as for the comment that 44 psi is absolutely incorrect--that's a bit misleading. 44psi may be correct, depending on vehicle load. The factory rating is the minimum pressure that you can run with the standard vehicle load. But tire manufacturers generate weight/pressure charts that show the pressure you should be running with any given load. So if you're carrying a heavy load or towing a trailer, in theory you should have more pressure in the tires. Within certain limits, the correlation between load and pressure is linear. For example, if a tire is rated for max load of 2000# at 40 PSI, in theory, if you're only carrying 1500# on that tire, you could likely run 30 PSI. Again--that is the theoretical correlation. The practical part of it is simple--Toyota recommends a certain pressure based on expected load, and a tradeoff between weight-carrying and comfort. With low profile tires, the comfort gained with a slightly lower pressure is minimal, if even perceptible. If you're carrying more weight, you need
more pressure. If you're not carrying more weight, but want to reduce rolling resistance and improve fuel economy, you can do so, provided that tire profile is not adversely affected. In this case, I don't think tire wear will be adversely affected based on my study of this car, and I've decided to run more pressure...a decision which is not "absolutely incorrect".