Basically the CLS is a prettied-up E-Class. Same platform, same mechanicals. The overwhelming percent of electronic gizmos are the real weakness of this car. Beauty is strictly subjective. But MB has a big, uncontrollable problem area: the electrohydraulic brakes. When the SBC lamp goes on, you have only the emergency brakes which can provide max. 0.3 g of deceleration and only the front brakes are working via a small, conventional booster. Because it is working only on the fronts, you don't have ESP & ABS functions, neither BAS (panic assist). This led to a massive recall campaign. MB updates the software and the problem can disappear. But it can stay as well, and in Germany there were a few cases when the car crashed almost immediately after the update. MB will discontinue this system as these models (E, CLS, even the SLR) run out. Not too trustworthy...
I would choose a Lexus GS450h or an Acura RL instead. For me, a spiced E-Class doesn't mean real premium just because the sexier sheetmetal. It is wiser to choose a more honest, less arrogant product. But obviously, if you want to spend lotsa coinz for a car... Honestly, with these mergers, we have no truly independent manufacturers any more (one exception is Honda). Everything is getting more and more diluted. And when only 95% of the purity is there and the vital 5% essence is missing - you won't be a satisfied customer.
