Experiences With 2006 Engines?

Was wondering about the new engines, 3.5 and 3.9. As I recall the 3.5 is all Aluminum, not sure about the 3.9. Any experiences with these engines, good and bad?. Have a 2005 Impala with the 3.8. Great engine. Thinking about a 2006 w/3.9. Not sure if it is a good idea to buy this one as it is the first year for it.

Found a good site for info. on current GM engines.
http://media.gm.com/us/powertrain/en/product_services/r_cars/car%20eng%20trans.html
Found out that both the 3.5 and 3.9 L engines are Iron blocks, Aluminum heads.
they have roller lifters, timing chains. Another new thing is the variable cam timing, they use a tubular cam. The 3.5 is flex fuel, 3.9 is not. Also they said the only difference in the 3.5 version(Canada) that is not flex fuel is the fuel rail and injectors. The injectors in the flex fuel, have a special tip coating on them.
Still would like to hear of any experiences with these engines.

I don't own a new impala, but have driven several, as I work at a parking lot. The 3.5 feels smooth, but not all that powerful. The 3.9, on the other hand, is very quiet, smooth, and feels like it has a lot of torque (never tested above 25 mph, though). I never drove a 5.3 impala, but have driven a trailblazer with virtually the same engine (only minor differences due to truck platform and longitudinal mounting vs. transverse). It's wonderfully smooth and powerful - best engine by a long shot. As for reliability, the only thing I know is that a test one in an article in the newpaper had the water pump go out at only 30,000 miles - not the reliabilty of the good old 3.8 . If I had to say, the 3.9 actually feels a lot like the 3.8, except smoother and more powerful.

I just bought a 07 Impala SS yesterday. The power and acceleration with the 5.3 in this thing is nothing short of amazing. It's like a stealth fighter on the street. The looks really dont reveal the beast under the hood. The SS doesnt really look that aggressive, more like a sporty family sedan,m but anybody pulling up beside me in a Camry, Accord, Maxima, ect thinking they can take me are going to be very, very surprised.