I drove the M-B E350 and BMW 535i last weekend at the BMW Ultimate drive event. BMW was so confident that they brought out one of their main competitors...and it backfired on BMW.
The M-B E350 was very smooth, everything from the transmission to the linear response from the V-6. The handling was excellent with pretty much no roll.
I tested out the handling on a long turn which was almost a full circle. The M-B cornered flat and predictable, even when I floored the throttle mid-corner. In the BMW there was tons of understeer through the same corner. BMW is really losing sight of its core competencies which made their cars so much fun to drive. M-B on the other hand is starting to make some incredible drivers cars.
I still prefer the exterior of the BMW 5 over the E-Class.