I think for me it's a combination of effects similar to the descriptions of others, although my delusions and psychosis are milder, and have, in the past taken on several "formats".
I am a physician, and basically all my waking life is dedicated to academic pursuits, therefore when my hypomania starts it usually does so with unbridled creativity and cognition. My memory improves, I'm the center of attention of conversations, I'm better at problem solving and pattern recognition. It feels like my IQ actually goes up.
But it doesn't stay that way.
Hypomania de-volves into mania. With delusional thinking that I see a hidden order and conspiracy in the world around me, with believing I'm the most intelligent being on the planet, racing thoughts, smoking pot (I don't have access to other more destructive drugs), and very hypersexual with risk taking behaviors that would end my marriage should my wife find out.

So far I've kept it together with my meds, but occasionally I hit a bump in the road that throws me into a depression or hypomania/mania and it's all I can do to keep the boat from sinking. I have a lot to lose if it does and my pdoc warns me of that b/c insight is the first thing to go with an acute state.
In my past I've been psychotic, thought satan and God were trying to recruit me for agent/double agent status to work in heaven and hell, but I remained high functioning so I wasn't institutionalized. That was my early 20's, although my first major depression landed me in one twice when I was in my mid teens.

I'm basically together, and ticking as best as a clock with a faulty mainspring can be expected to.

Abilify 10
Lamictal 100 BID
Lithium 1200
wellbutrin 300
prozac 20
Propranolol 160SR
primadone 50