I have experience primarily using InRoads with some exposure to GeoPAK. GeoPAK to me seems very clunky and outdated. It bases everything off COGO and the methodology to me is equivalent to what was cutting edge when computers first were used in drafting design industry-wide in the 90's and manually programing steps was exciting and cutting-edge. While the vast majority of graduating engineering students have experience in nothing but AutoCAD, Microstation and InRoads are becoming much more compatible and comparable to AutoCAD users with each version, reducing the learning curve for new users.
There are significant changes between the most recent versions of Microstation and InRoads, improving each time. Those significant changes come with a learning curve, as anything would. The latest release, Select Series 3, completely revises the interface. InRoads becomes part of the task bar, eliminating the need for a separate window InRoads used in Select Series 2 and all previous versions. In advance of learning and using SS3, I strongly recommend switching from tool menus to the task bar layout while you're still in SS2 so you are more comfortable with that approach when you switch.
Modeling tools are powerful, especially in SS3, however models can only get the design to a certain point and fine-tuning by hand is inevitable which will probably always be a fact of life. As users gain experience, they learn tricks that can help eliminate surface errors such as around street corners and intersections, islands, and roadside terrain. The OpenRoads system in SS3 is much more streamlined and user-friendly compared to SS2.
There remains a significant learning curve for recent graduates or new hires whose sole experience is in AutoCAD, and even users switching from GeoPAK to InRoads.
SS3 reduced the complexity of steps necessary to complete design tasks, but all the options and steps (a result of the power of InRoads, now OpenRoads) can bog down novice and amateur users until they become more familiar with the capabilities.
AutoCAD has many interface features that are much more user-friendly, which are apparently copyrighted because Microstation still tries to incorporate them in their own clunky way (key-ins that are not as easy as in AC).
Additionally, too many people choose to tinker with code and create highly customized workspaces. Customized workspaces tend to be problematic and error-prone, and often eliminate standard tools and options built into Microstation and InRoads out-of-the-box.
Spend time learning the intricacies of the program. It is very powerful but can seem complex the first couple times when all you want to do is create an alignment or a roadway surface. As with anything, practice makes perfect.
Roadway and terrain surface modeling and modification. Time savings over manual or more cumbersome methods.