My dosage is pretty low (see my other reply), and I'll usually only take another 1x5mg which seems to 'top up' the previous dose for around 6 hours. EDIT: I believe they are considered 'quick release', described as active for 4 hours, though I seem to wind down after 5. (then I get a bit fuzzy for an hour, cant hold a conversation easily, focus gets locked on tasks I'm working on, etc...)

The general effect definitely makes me more alert, but doesn't keep me awake. On weekends, I'll often have a nap after my second dose, its like my mind clears enough to settle and without purposefully taking in new stimulus, it relaxes and I drift off. Some people describe the same with Caffeine.

As a side note, I drink coffee if I want to wake up / stay up late. Caffeine seems to turn off the part of my brain that says "fall asleep", increases my heart rate a little, but thats about it. My dex on the other hand, seems to raise everything a lot more evenly. It doesn't affect any one thing more than the others.

I'd describe Caffeine as a "dirty" feeling stimulant, and Dex as very "clean", as an anecdotal, personal comparison.