I just got one and have been playing with it for a few days before diving with it. I decided to get it even though it has a few limitations that I don’t like.
Once started, when locked for diving, you can’t stop it. It runs the entire dive. Kind of a trade off. You have to cull a ton of pictures or do massive editing on the video to cut out all the exteraneous crap. On the other hand it sees and records everything you do during the dive. You don’t have to pay attention and try to get specific shots.
It also can not be switched between photo and video modes when locked for diving. I think this is a serious flaw but one I might be able to live with. We’ll see.
The lens is wide angle and mounted on my mask strap half the picture was filled with the side of my mask. To be fair, I have a bulky rectangular framed mask. However, if you watch their video closely you will see the mask in the lower left corner. I can’t imagine they put anything other than the best shot they were able achieve, so I got to think that there is no way that the mask strap mount will allow a clean picture with no mask in it. As far as I know you can’t crop a vid. Could be wrong though. At any rate I was able to use Marine Goop to create a wiring cage on the side of my mask. If you don’t want any mask in your pictures and vids you better plan on inventing some way to mount it to your mask with the lens even with or ahead of the front plate of your mask.
The pictures are standard .JPG files. However, the video is in .MOV format. Is that a Mac format? In any event, it doesn’t play in Windows Media Player directly. You need to convert it with "Any Video Converter" or some such.
Another thing to keep in mind is that there is no way to review shots till you dump them to computer (and then convert if video).
I will be using it this Sunday on a couple of dives. That will tell me a lot. I’ll post Sunday night or Monday morning how it worked for me diving. I would not have bought it if my Powershot S500 haden’t died. Now I have to decide if I should sell the UW case, batteries, memory cards, and chargers for the S500 or keep the S500 equipment and find a replacement on EBay and sell the new Tachyon. Time will tell.