Simulations for mobile robots

What I like the most about robotic simulations is their sheer ability to make software development and testing process time-efficient. Working with robots (to a large extent on prototypes, and often remotely) over the last decade has helped me come up with a simple rule -- do as much as you can with the simulation, use the actual robot hardware when you absolutely have to. Software for robots HAS TO run on robots, there is no way around it. However, there is plenty of simulation-based testing that can expedite your route to software deployment on the robot, and robot deployment on-site. I've spent the bulk of my time working with wheeled mobile robots and my choice of simulators for application development and testing is centered around that.