Rhapsody provides an elaborate GUI for Systems modelling.
I have been a user for last 4 years and the following aspects interest me:
1.Harmony SE process : we can trace a requirement from concept to code using the exclusive profile meant for SysML
2.Simulink Integration : We can import a simulink model in rhapsody and generate the code from it.
3.Rhapsody Eclipse Integration : Probably the best feature of Rhapsody is that it can be used inside eclipse as a perspective. We can Know the code behind every Model element.
4. Java APIs : Another best aspect is that we can automate practically everything using Rhapsody Java APIs
I use it in Architecture design of Automotive embedded systems and products.
I find it easy to use and modular as it is OO based.
We can make a layman understand the mechanism behind the code using its diagrams (flowcharts and Statecharts,requirement diagrams etc)