The Lancet has a comprehensive review of bipolar disorders- finally I learned about the distinction between type I (includes mania) and type II (hypomania). BTW the author thinks that there is no sound evidence for the DSM-IV priority for mood changes; Kraepelin had no priority for mood, thinking or activity altering changes after all).
It seems that some scientists, at least those succesfully organizing large units, have symptoms that are described by this paper

included creative thinking (more goal-directed, structured planing, more brilliant ideas), crowded thoughts (non-stop thinking), racing thoughts (speedy thinking), and flight of ideas (quick, disconnected thinking).

Hypomania does not seem to be simply a mild version of mania as I thought before. It is an own entity as found in longterm studies. Mania has always 4 or more symptoms, lasts longer than 1 week and is often accompanied by psychotic symptoms that are never found in hypomania. Increased energy, talking, thinking, high self-esteem and psychomotor activity and decreased sleep may be found in both.

overactivity is the core is the core feature of hypomania […] more than usual working hours […] can increase functioning if the concurrent mental overactivity is connected (as often happens)