Well, the jury is still out on dendrobium. There's really not a ton of safety research on this stuff, at least not for long-term consumption. It "seems safe" though, when not adulterated with other nonsense.
But note that this product has stimulants, and stims will generally elevate your heartrate and raise blood pressure.
Also, there's PEA, which should NOT be mixed with certain prescription drugs (like MAO Inhibitors). It depends on who you are and how your brain functions.
Overall, it's a pretty powerful supplement with a few new ingredients. If you're worried about safety, stick to one scoop or go for something older that's a bit more benign.
That said, it doesn't show any effects like DMAA does... and if you've used a few other pre workouts and want the next level, this could be it.