Pros
Massive multi national with a very diverse product range. The name Siemens opens many doors in many industries. The products are known to be good quality (like your Mercedes Benz type product). Very top management (Germany) appears to be strong. Local top management is also strong however when you drop down literally a level or two competency of management can be appalling. The culture depends on your division - Like any large company there are many people who bring positives and negatives to the organisation. My division has almost always been positive.There are people around that do want to go the extra mile. The trick is to find them so that you can do your job. Starting salary was really good, this stayed relatively flat after that. Training opportunities are there for the taking. Travel both local and international is an absolute possibility if 1) wanted and 2) you are in a position that facilitates this. All in all I love Siemens, and feel privileged to work here.
Cons
Not always too easy to progress - There is a boys club mentality and often people get promoted without any job advertising taking place. Negotiate hard on your starting salary - you cannot rely on your increases. Commission structures literally change on an almost annual basis - therefore goal posts keep shifting. There is a chance to find yourself under a bad manager. In my teams case, the organisation has been much too slow to react to bad middle management. I cannot emphasise enough how a poor manager has tainted my view of the organisation, and most of all that not much has been done by senior levels to alleviate this.