*ding*
We have a winner!
As for the 3800...it should be gone. Those arguing in favor of it only have the arguments of "reliability and well it appeals to traditional Buick buyers"
Buick needs new customers, the "tradional buyer" is getting older, and won't being any new traffic into the showroom. Also, as other have mentioned, the 3.6 seems reliable so far.
3800 w/ 4-speed is all well and dandy...in a base Malibu or something. This is supposed to be a "premium" car, it should have a more "premium" engine. When the Malibu, Aura and others that cost less than the Buick have an engine that makes nearly the power of the NorthStar yet gets better fuel economy...who is the fool for buying the big, slow, expensive car? If Buick wants to be taken seriously, they need to compete seriously. 3.6 w/ 6-speed looks good on paper and performs well in the real world. The 3800 may be "good enough" but it's nothing eye catching...and I could get more power out of a cheaper car. Add to that an interior that's exactly "premium" in many ways, and you've got an outdated piece of machinery that doesn't help Buick at all.
If you want to keep the 3800, fine...make it the base model or something, but the 3.6 should be optional and standard on the CXL.
You could at least bolt a 6-speed to the 3.8...there's no excuse for not having one.
As for the NorthStar, Fly makes very good points, as usual.