I have one, it is an interesting firearm for sure. I'm a relatively small framed guy and bullpups fit me well. I have a number of them including an X95 and a keltech ksg. I love the x95 and I love the ksg so I figured I would love the TS12. I don't hate it, but I don't love it.
I got the gun used with a couple hundred rounds already through it so it was already broken in. I have not had any reliability or running issues with it, but have heard of plenty of people having issues before its broken in (~300 rds of heavy high brass loads).
It shoots nice, very smooth but not super easy to operate. The rotating tube mag is a bit fiddly and I found it somewhat easy to roll it right passed the next tube when operating quickly.
In my experience, it has not been super accurate. The top rail is mounted weird and seams to move around a bit. I wouldn't try to hunt with it, but good enough with buck shot.
It is fun, but would grab the ksg before the ts12 if I had to choose one.