The Simotion C240 can be programmed in Structured Text, Motion Control Charts (like S7 Graph but more advanced), Ladder/FBD and Drive Control Charts (CFC for Simotion). It goes without saying that it does camming,gearing, interpolation...etc...The scan time is fast enough to create your own blocks and call them from motion control tasks or a few dozen other type tasks if you wish.
Yes, you can treat this controller as just a fast PLC too.
Simotion is programmed with a package call Scout. This programs all the functions for Simotion plus the drives (Siemens Drives). Scout can integrate with Step7 too, but it is really just launched from Step7 and again all the tools reside in Scout.
Have Siemens come in and give you a demo. This system is very nice and fast.
I know its alot cheaper than the FM458 plus you need D7-SYS for the 458.
If you like the CFC for the 458, you will see it in Drive Control Charts for Simotion.
I would recommend taking a class but if you go through the "Quick Start" manuals and take your time, a 2 axis application should be pretty easy.
I hope this helps
http://www.automation.siemens.com/mc/mc-sol/en/e81063c5-bdca-11d5-86dc-080006278927/index.aspx