The problem in Munich is that everything must go through a single two-track part underneath the city center, which is at absolute capacity. If anything breaks down there (and it does, often, very often), even a small delay in a single train, all trains get delayed or skip stops.

In my experience, you have to take at least one train early if you do not want to come late regularly. Even e.g. the main airport train line, used by tourists, often turns around before the actual airport due to delays.

If you live in the city itself, it's fine, you also have other options. If you live further away, it's barely acceptable to very bad, IMO.

It is reliable-ish, but more "Amtrak Capital Corridor"-reliable than "JR Yamanote Line"-reliable.