Who should buy a Weighted Gimbal Stabilizer
The Glidecam HD2000 is a weighted gimbal stabilizer.  It uses inertia of a counter weight and a balanced gimbal to prevent rapid changes in orientation and to an extent position of a camera.  They are used for stabilizing footage when you need more stabilization than optical image stabilization can provide but less than a steadicam or gyroscope rig provides (or the cost or size of a steadicam or gyroscope unit is prohibitive).

Unlike optical image stabilization, a weighted gimbal rig requires a fair bit of practice to master the use of as well as careful configuration and balancing to prevent the system from drifting.  A handle is attached to a near frictionless gimbal at the center of gravity so that the handle can move without the camera moving significantly.  It requires careful handling and manipulation to control the camera's angle while also requiring quite a bit of strength to hold the handle at the appropriate angle.

The main pro is that it provides far more stabilization than optical image stabilization, is relatively compact, light (roughly 50% heavier, though if you use monitors and such that can be used as counterweight ) and low cost (compared to more advanced stabilization systems.)

The main con is that it still adds quite a bit of weight to the camera rig.  They are difficult to use well and require careful movement and handling to get good results.  They also require far more physical exertion because of how you have to hold them (hard on your wrists.)  They also do not provide nearly the stabilization of more advanced systems such as a steadicam rig (chest support plus weighted gimbal) or a gyro-stabilized system (with high speed gyroscopes actually actively countering changes in orientation).