I have a 2003 E320 211. Brakes work great. Never had a problem. Yes, there have been recalls but for obscure things. One of them involved putting a 10 cent plastic cable tie on the cable to SBC pump (and a metal thing for it to attach to) so that it would not get unplugged easily. Another was to provide something after hundreds of thousands of brake applications which was really only ever reached by taxi drivers in Europe. People also complained about the noise that the pump makes but I never thought it was excessive. I am not sure it was a recall, but if you complain, they put a damper on the pump to cut down on the noise.

Again, the system works great, I have had zero problems after 25,000 miles.

Some people complain about the feel of the brakes. After a few miles, I doubt if you notice the difference unless you want to notice it. It may not be quite the same feel but you get used to it. My wife has never, ever said anything about the brakes feeling different.

Although I have read of problems, I have never met anyone who has had SBC system problems. But I have heard of problems with more conventional brakes so I suspect all systems have some problems.

Only thing I dislike about it is that if you change your own brake pads, you have to do it in a certain way to avoid blowing the pistons out of the brake cylinders or getting your fingers pinched. But even with this, there there is a way to do it safely and if you are interested, I can provide the links to doing it without any specialized equipment including the Mercedes official way (others have a more simple way).

I am not sure of the cost benefits of the system but Mercedes claims it only costs a few dollars extra for the system but that may have been before the recalls. And if I had the choice, I am not sure I would want it but it does work great.

In short, do not worry about it. If you drive the car and like it, buy it. If you are really worried, buy an exteneded warranty. I have an extended warranty but not because of the SBC system. There is a lot of other electronics in the car that are just as complicated or more complicated and if you are worried about SBC, you should be worried about those systems as well.