I personally think that Siemens doesn't really like ladder, just as A-B doesn't really like sequential function chart. They do it, but their hearts aren't in it. Siemens grew up being programmed by and for engineers, A-B grew up being programmed by and for electricians.
Having said that, the transition is only moderately painful. Variable naming is more painful in Siemens, and the monitoring functions are more difficult. However, you can do anything with Siemens tha you can do with A-B. Siemens documentation is not as good, since it is so volmunious that finding the info you want is tough. JRW had a good suggestion, and I suggest you cultivate a relatinship with your local distributor as well.
The key to going to any new platform is to phrase your question properly. Don't ask yourself "What is the Siemens equivalent of this Allen Bradley function?" Instead, ask "How do I perform this task or operation in Siemens?" The difference is subtle, but will avoid a lot of confusion. Instead of translating A-B to Siemens you will be learing the Siemens language. Just like a child learning bilingual skills, it's easier that way.