If you follow the instructions it's great, if you heat it too much it in one spot will catch light, but it will extinguish itself soon as you stop sucking and you can vape the rest.
I'll get round to posting some pic's to show what I mean.
Bubble or any other hash is difficult to combust with this thing, and gives great vapour.

Like any tool it takes practice, who hasn't hit their thumb with a hammer or cut themselves shaving?