My tolerance is clearly up there.
I have been leaning more heavily on deriving energy from 1,3 DMAA than caffeine around the workout, at least when I'm sleep-deprived (as I was yesterday). I by no means rely on stimulants, but when I'm sapped and sluggish 1,3 kicks it in the ass harder for a power day, which is what I look for.
3 caps of 1,3 DMAA provided an intense but very smooth kick in the ass. I didn't crash, and I don't experience negative sides with it typically. If you're well-suited to 1,3 DMAA, I wouldn't be concerned. I would definitely work up to it, though, and not do it often. I was going for massive PRs last night, including a 3x5x405 SLDL, so I wanted a little extra "push". Like cocaine lite.