So, just what are we talking about?

[kandrathe]

...but why omniscient and omnipresent?

If God is not bound as we are by time, then all past, present and future events are simultaneously known to God. This is an understanding of God that is "transcendental" to the reality known to mankind. Similiarly, omnipresence, can be ascribed either by the former extradimensionality (or nondimensionality) of God, or for some, that all reality is God. That ties in more with the later part of your question of pantheistic beliefs, where some religions hold that spirits or separate godness inhabit every existing thing, including plants, minerals, animals and, including all the elements, air, water, earth, and fire.

What if god is 'Murphy-esque' and hence not omnipotent either?

Ok, trying the make the intuitive leap here, but I assume you mean that God means well, but somehow if something can go wrong it will. I guess all I could offer would be to suggest that most philosophers make the assumption that a "God" by definition would be the representation of our understanding of perfection. Deism holds that God is above intervention, and theism holds that God is both transcendant and yet involved in our daily lives.

An example would be in the classic Aristotlian definition; Aristotle -- Metaphysics

In the "Metaphysics" Aristotle proposes that the actual is of its nature antecedent to the potential, that consequently, before all matter, and all composition of matter and form, of potentiality and actuality, there must have existed a "Being" who is pure actuality, and whose life is composed of self-contemplative thought (noesis noeseos). The "Supreme Being" imparted movement to the universe by moving the "First Heaven", the movement, however, emanated from the "First Cause" as desirable; in other words, the "First Heaven", attracted by the desirability of the "Supreme Being" -- "as the soul is attracted by beauty", was set in motion, and imparted its motion to the lower spheres and thus, ultimately, to our terrestrial world.   Accordingly, then God never leaves the place in which his blessedness consists. Will and intellect are incompatible with the eternal unchangeableness of his being. Since matter, motion, and time are eternal, the world is eternal.