PureVia is not stevia. It's an stevia extract (rebaudioside a). Stevia is supposed to have some benefits, like improved insulin sensitivity. Some people tried to see if reb a has the same benefits that stevia has, but the studies show that it doesn't.
1 week after I started consuming reb a, but in the form of Truvia, I woke up and my automatic breathing stopped (so I had to breath voluntarily). Soon after I was having a panic attack, for the first time in my life, and went to the hospital. Normal breathing returned in a few hours.
I stopped consuming Truvia for a few days, because I ate many other new foods at that time, and was trying to figure out which one triggered it. I didn't have any other panic attack for a few days, so I said, it was probably a one time thing. I drank something with Truvia that night, and at 6 a.m. I woke up again with my breathing paralyzed.
What happened to me doesn't seem to be abnormal. I googled stevia, panic attack, and found somebody who had almost the same experience as I did. Check this guy's experience: http://forums.lowcarber.org/archive/index.php/t-109690.html
I believe not everyone will be sensitive to it. I was hypothyroid at the time, which can increase the risk of SIBO or gut problems. I think it's in that environment that Reb A (Truvia, PureVia) can be most harmful.
Reb A doesn't have any benefit that Stevia doesn't. It's probably worse than Stevia. I think the main reason companies sell it in the Reb A form is that Reb A can be patented, while Stevia isn't, so if they find some benefit of Reb A, like maybe extra sweetness, nobody else would be able to sell it.