THIS is the BIGGEST problem with many of you people. You are all so brainwashed into thinking that OHC engines have NO low end power and are extremely peaky while OHV engines are the end-all be-all of low end power. This is just plain wrong.Torque is important in far more than trucks. We aren't talking about 2000lb sports cars here. We are talking about med to large sedans hauling four adults and their luggage. A 4V motor may feel just fine tooting around by yourself, but as soon as you add any significant load to it, the car will feel and be significantly slower. The only remedy for that is torque and easy access to it, which the 3900 has in spades.
The Northstar has a very linear power curve with plenty of power available at any point in the rpm range. The 3.6 VVT is quite similar, with 90% of its torque available as low as 1600 rpm and peaking at 2800 rpm. Nissan's 3.5 liter V6 has a very broad power curve as well.
Take a look at Nissan's new 5.6 in the Titan. That has more low end torque at a lower RPM than all of the OHV engines GM offers in its pickups (save for the 8100).