It's the sort of thing you'd have if you had to work 18 out of 24 hours a day, and you really needed to push yourself that little bit further. I personally like it, but beware of having more too soon (infact don't redose for a long long time) as you'll get quite anxious and you'll feel rather tense to say the least. I suppose it's also good if you want to go out and be awake, but not feel like you've had anything.
I give it a 6-7 out of 10.

I'd still prefer speed tbh, but it's a good replacement I suppose.