nice comments. here's my difference

Lexus is almost like your saying, and in addition, its styling is way too aged except IS. The seats for me are too soft so I got tired easier, so it's not comfortable for long distance.About the IS, it's so cramp for...any distance.
The Mercedes...yeah, it's safe, comfortable, luxury and superb dynamics in high speed and it tends to everything just nice. I heard its reliability has improved much since 2007. It's the kind of car lexus wants to follow and it's still leading, including sales.
The BMW...actually it's kind of flexible. It could be driven like F1 but frankly it's still comfortable, in my experience even the most pumpy ones, the 3 series, still less pumpy than Audi A3,A4. The 7 series are damn comfy, only a bit shy to the S-Class, yes, more comfortable than LS,XJ and Q45, didn't have a ride in Audi A8 yet though. The 650i convertible is comfortable but less fun than 335i conv.
Audi, got almost the same as yours and it knocks Lexus out of the world's top 3 premium brands in terms of sales and pulls away, probably surpassing MB in several years. In compact car segment, like I said, 3ers are both more comfy and better handling than A4. That's where it needs to climb hard.
Infiniti's G is better than lexus IS. lexus LS is better than Q45. Unlike lexus following MB, Infiniti wants to follow BMW. That's it.
Cadillac, I like the CTS and Escalade, but not as impressive as 3ers and GL.