I've been using a Tria for about 9 months. It has worked really well on my arms and hands. It hasn't worked quite as well on my chest and stomach. There is some reduction, but a lot of hair there on me is intermediate between peach fuzz vellus hair and terminal hair. It is dark and somewhat long, but very fine. The Tria seems to work better on thicker hair follicles.
Although the newest Tria can be used by women on the face and neck, it is not recommended for use on beards because the concentration of follicles can cause burning of the skin. I've ignored the warning, because that's main reason why I bought it in the first place. I have seen some reduction on my neck and the sides of my face, but those areas were always pretty sparse for me so I can use the highest level, level 5. I can't really tolerate higher than level 3 on the denser areas, especially the upper lip.
I may just go to electrolysis for these areas soon, I'm disappointed of how little progress has been made on my face, and I absolutely hate wearing foundation. I don't see myself ever being comfortable wearing it in public. One sneeze and it's a huge mess and my stubble is revealed.