I took the "Training with PC Based Simulations" elective at CGSC in APR-MAY. We were introduced to everything from FPSs, through small unit stuff (Follow Me, TACOPS and Steel Beasts) to large unit level sims (DA, etc).

Each sim has its uses and limitations. As long as you understand the sim, and use it to train appropriate training objectives, they are great tools.

The biggest issues I see are:
1- senior leaders that don't accept the validity of training
2- the "learning curve" required for some sims (the more "realistic", the steeper the curve)
3- lack of leaders understanding how to train with sims
4- the possibility that budget cutters will forego live training for sims. Sims can meet some objectives, but the final edge has to be honed with live action training- you can't simulate the sights, sounds, heat, fear and exhaustion of combat, but you can come pretty close (everything except the fear) in an environment like JRTC.