I own the GT2541EX;

The positives;
It can be manipulated in to any position you want and is very versatile. I have used it in configurations that have held the camera out over the side of cliffs before. (try that with your standard three legs)
For macro (which is why I bought it) you can shoot under over and around the legs.
It is solid overall.
The legs adjust easily and quickly to different lengths and the lock is very positive.
The lever that tilts the legs can position them at any angle you want.

The negatives;
As a backpack tripod it will be heavier than other models.
Watch the feet, they screw loose. I have heard that some people use lock tight on the threads. I just keep a few extra.
It is a bit shakier than others when vertical, only because your lens is offset from the center of the tripod. The arm connects to the side.
This side mount gives you the ability to do odd angles, the shakiness is a small compromise.

It is a great tripod, especially if you need something very creative. If you are backpacking, traveling or just need a general tripod others may be better when weight matters.

Consider this tripod a specialty tool, because that is what it is.