FINALLY!
I got to test drive a silver 2.8 Turbo sport luxury. I picked it up last night and I will return it tonight. I drove it from Hamburg to Berlin (200 miles) last night (to my gf) and back this morning. So here is my experience:
Like I said before, the room for the driver is not much smaller than in the CTS. There's even more leg room and the steering wheel has tilt and telescope!
In the city it drives well. You have a good overview on traffic and it handles tight and direct. The seat is very comfortable, also on long stretches (lumbar support is manual). The seat and mirrors have 3 memory settings. I just miss a little more support on the sides of the seats. The sports version could have some deeper fit so you wouldn't slide in the corners (as it curves like a knife). Hardly understeer unless you apply too much gas in the corners (front wheel driven).
Of course I tested the top speed on the Autobahn. I topped at 255 km/h (160 Mph). The acceleration is better than the 3.2. I can't say for the 3.6. When you floor it at 0 it seems hesitate a little, but that's only a 1 second turbo lag. Than it kicks in and you fly away. The motor sound at low rpm is a nice deep tone. Not loud, just barely noticable. Nice! When you floor it it roars (slightly higher tone than the 3.2). Actually, the engine sound is less in the BLS than in the 3.2 CTS. But I had a sunroof and the wind noise is a lot more than in the CTS. With the CTS I notice more wind noise at the mirrors and the lower part of the doors. In the BLS it's the sunroof. Anybody with CTS sunroof?
The suspension is noticably stiffer than the CTS. Very sporty but not uncomfortable. I had to get used to it as it sticks to the road. At high speed you have to be aware of bumps. They will not be evened out like in the CTS. So road feel is good, if you like sporty. I liked the braking of the BLS more than the CTS. In the CTS the brakes tend to shutter at higher speeds. The BLS brakes keep smooth. The brake handling is different though. Braking abrupt at higher speeds the BLS tends to sway more than the CTS.
I also checked the reaction of other people on this car. It's a new model, but not many people seem to notice. A lot different than the CTS! On the Autobahn a silver Benz coupe, a black BMW and a black Mini Cooper S wanted to keep up with me, but couldn't

In the city at the traffic lights I had some few people looking at the car, but no real head turners like with the CTS. It's not a big car and the lines are not as daring as the CTS. Even the STS front wouldn't really turn heads here. If you want to blend in with a high quality sports luxury car over here, than this is a very nice car for you!
In my opinion this car competes with the BMW 1 series, the Audi A3, Volkswagen Jetta. No headturners either. It shares it's platform with the Saab 93 and Opel Vectra. It's only a few hunderd Euros more expensive than the Vectra.
For the US market? Well, the Saab and Jetta sell in the US too, right? So why not? Fuel prices keep rising, so a small diesel Cadillac might be welcome again in the US...
Sorry, pictures and films follow tomorrow. I finally get my internet back then after I moved 4 weeks ago... slow bureaucratic system...