At the time of it's creation, the Northstar was a big technological step for GM. Designers incorporated an aluminum block, dual overhead cams, and a unique "limp-home" feature. This protected the engine from overheating, even when driven up to 100 miles with no coolant. Most variations were tuned for an output around 300hp, or a little less. I can attest to the strength of these motors, having owned a 1997 Seville STS for several years. Those are by no means a small or light car, but the Northstar will get them moving in a hurry. Another thing that always impressed me about the motor was it's fuel economy - nothing to brag about around town, but excellent on the highway. I got upwards of 25 mpg on several highway trips in that car. The more I drove it, the more I appreciated the performance of the Northstar.
It's hard to say why exactly why they would end the life of a successful powerplant, other than the industry trend toward 6 cylinders. These days, manufacturers are advertising V6 engines producing 300hp and getting 30 mpg on the highway. Add to that the fact that they are lighter, and take up less space, and it's hard to make an argument against them. Overall, the Northstar has lived a good long life and has gained many fans - myself included. It's spirit will surely live on in GM engines yet to come.
[General Motors via Inside Line]