Pros
Opportunities - tons of them. Chance to travel and work overseas. Company is well known, maybe for its legacy systems but it is the 800 lb gorilla. Working in a 50,000 employee company can be a bit daunting however the converse means plenty of opportunity. I think it comes down to "think globally, act locally" by this I mean it's who your immediate management chain is that will really make or break the work environment. Maybe this is obvious but this mitigates the fact the company is so large. The benefits are also extensive and the company takes care of its performers. A critical view of any company is how they handle the top 10%. This may seem elitist but if you don't take care of your top 10%, you will find them elsewhere. SAP understands this.
Cons
MRP, ERP and any other 3 letter alphabet soup systems can be like chewing chalk however the amount of sophistication and technology required to get this stuff right add some luster back. Regarding company size, this can be daunting almost like you need a map. This makes it difficult to determine the interfaces and moving parts in any strategic effort as there are many stakeholders whos intent has to be gauged and accounted for. This just means you have to be more astute and organized if you're dealing with senior level work. I guess this would apply to any large company and SAP being a German company means you must be culturally aware.