Many people take caffeine always, or never. But the evidence is clear: for some tasks, drink coffee -- for others, don't.
Caffeine:
- Impairs hippocampal neurogenesis and long term memory
- Narrows focus -- aiding short-term memory when the information is related to the current focus of thought, and making short-term recall more difficult when the information isn't related
- Increases short term recall of both true and false memories
- Increases short term memory and attentional control
- Increases memory retention and retrieval
So:
Use caffeine for short-term performance on a focused task (such as an exam).
Avoid caffeine for tasks that require broad creativity and long-term learning.
(Disclaimer: The greater altertness, larger short-term memory capacity, and eased recall might make the memories you do make of higher quality.)
At least, this is my take. But the issue is convoluted enough that I'm unsure. What do you think?
Your summary roughly matches my own research and is confirmed, for what it is worth, by my own anecdotal experience.
I'll note that similar (but stronger) effects can be expected from the more direct stimulants (amphatamine, methamphetamine, etc.).
ETA: Regarding attention control, be aware that sometimes increased 'attention control' comes in the form of increased focus on the immediate task which can actually reduce the ability to switch tasks smoothly. This can affect the balance of attention you place on social details relative to task details when the situation at hand requires both.