This is my second lexus moving up from the ES. I test drove the Audi and while it was definitely more sporty, I ultimately came back to the GS. The interior is roomy and packed with features. The GS does not have the tight suspension the A6 has, but it corners well, and has great pickup. As with my previous lexus, the build quality is excellent, and the car is just a blast to drive.
Bluetooth, nav system/central screen controls, keyless entry.
Pop out control panel is impossible to use when driving, save your money on the mark levinson system; I didn't notice any difference between that and the regular system - and it still has a cassette tape?? Come on!