I have a gigapan, the classy model. It is a real mixed blessing.
First of all it works. Once programmed it will move the camera about automatically creating a series of files that its software will integrate into a panorama. Now that is the good news. There is more.
To do a proper panorama you need to have the optical centre of the lens over the rotation point. I found that was impossible for some of my lenses. The rack didn't adjust as extensively to cover off all my lenses. That said though, I was able to use two.
I had problems getting a set. The gigapan doesn't just move the camera about, it also trips the shutter. I was using it on a D200 and on a D3, there was a cable for each that connected the camera into the gigapan. In the course of doing a dozen or more images, once in a while it missed one and just went on. Why it wouldn't trip the shutter in those instances I never figured out. Going back to take the missing picture is a problem as I will explain.
The device comes with software, the classy version on trial. The trial ends after a month leaving you with the starter version instead. When I first started using it I found basic functions like cropping and adjusting contrast and exposure impossible to do. I wrote Gigapan about this and was unhappy, the software did not have those functions.
So I asked what the classy version for $150 at the time could do, could I get the functionality there? The answer was no, I was using the classy version as a trial at that moment. Why would I spend $150 for pathetic software when I can get a full blown editor for half that price?
When it came to assembling the images the software was fast. Photoshop was like a turtle with lumbago in comparison to the performance of the gigapan software. But when you were done you didn't get a JPG, you got a TIFF and then only if you selected that option before you started. Otherwise you got a proprietary file that was useless outside the gigapan world.
Then I discovered the next issue. The images are processed in the sequence taken so if you're missing an image in the set you get a distorted result. The software does not take into account missing images. It also won't accept missing images if you go back to quickly snap them too and include them in the set. To use those you'd have to renumber the set of images so that those new ones are in the correct slot.
I sent them a number of complaints and suggestions for improving their software but nothing ever happened.
So, I don't recommend this product at all. I do sometimes use it for panoramas but only rarely and then I use Photoshop to assemble the image since that also gives me typical editor functionality that gigapan refuses to provide. Using Photoshop also gets me JPGs as well as a variety of other industry standard formats.
As to whether they still exist, I haven't seen them in the camera shows for the past three or so. Their web site still exists ...
http://www.gigapan.com/cms/manuals/epic-pro-introductionso maybe it is still around.
As to alternatives, Manfrotto has a panorama head for a tripod. it has the flexibility for setting lenses on their optical centre. It has detents to ensure effective overlaps. And it does a good job. It took me some time to figure out how to use it but once that's been figured out it does an excellent job. The only difference is that you have to do this manually instead of automatically and of course you need to use Photoshop for the edit.
There may be other solutions but I don't know about them.