While I love the Gigapan Epic for shooting panorama photographs, it is not a perfect device.
The Epic, and I believe the Epic 100 from one of my readers who has taken his apart, is built to a price and has sloppy bearing surfaces that mean there is plenty of movement on the two axes. Most of the time this causes no real issues, but it can. What I mean by looseness in the axis is that there is both some rotational movement and some tilting movement about the two rotation axes on the unit.
With anything except the very lightest of cameras the vertical rotation axis that is used to tilt the camera up and down can sag. This means that, even if you carefully use the spirit level to level the Gigapan before your panorama, the camera will not be perfectly horizontal, as you can see at the bottom of a panorama below.
Whilst this does not seem to be an issue with the Gigapan Stitcher software (apart from giving the ragged edge around the panorama) I have been experiencing some issues with stitching panoramas with other software. I am still investigating this.
Related to these issues with other software (so I can stitch using the RAW files, rather than just the JPEGs the Gigapan software currently allows) is wind sensitivity. When I have been out shooting in heavy wind conditions I have seen quite a bit of camera movement about both axes as the wind load on the camera has shifted. I have not yet determined if this is a cause of at least some of these issues I have experienced.
One related area of concern is leveling the camera. The Gigapan has a built in spirit level in the base. However, I have noticed that if I level the camera and then rotate the Epic 90 degrees or more the base is no longer showing as level. This is because the horizontal pan axis also has significant slop and this manifests as the ability to tilt the whole unit from side to side by a small but quite noticeable amount. With an off center weight, such as a larger camera, this means that as the unit rotates it can move off of level. Wind load can also move this. This could create image alignment issues across the panorama.
It is unclear to me just how much of the issues I’ve seen stitching some panoramas have been due to the above issues. These issues have not been with the Gigapan software but when I have tried using some other stitching software.