How helpful are Boson Sims and which path?

How helpful can the CCNA NetSim 8.0 help me with the CCNA labs for the exam? is it similar to the exam and does it give real live scenarios? Second, if I am planning to test for the CCNA in two parts ICND1 and then ICND2 does Boson offer a package to cover both or would best purchase seperate Sims?