One of the many features announced on the iPhone 4S is 1080p HD video recording. This is a nice improvement over the iPhone 4's 720p HD video recording.
The goodness does not stop there, however. In addition to 1080p, the iPhone 4S is equipped with video stabilization to help steady those non-professional, bouncy video recording skills.
Since the iPhone 4S video camera is the same 8MP camera used for stills, it will benefit from the larger aperture and improved illumination sensor, bringing you more accurate colors and better low-light videos.
You can see examples of the camera and stabilization on Apple's website. I encourage you to check them out, it really shows off how great video recording on the iPhone 4S will be.