I'm recording this as a reference for myself when I wake up tomorrow. (Conjectures ranked in order of how certain I am of them, from most to least)

Conjecture 1:
Of the set -- short, powerful, maintainable -- all computer programs exhibit at most two such characteristics.

Conjecture 2:
Programs which exhibit zero or one such characteristic have their programmer as a limiting factor.

Conjecture 3:
Programs which exhibit two such characteristics have their expression language as a limiting factor.

Conjecture 4: (which I would like to disprove)
It is impossible to construct a program which fulfills all three characteristics.