Seems like I have a quite different understanding of playing casters in D&D 3.5, hopefully this will bring some new aspects to the discussion:
Over my experience in role playing (expanding this to DSA and Vampire), the Mage archetype has the problem solver role in the party. To do that, he has to be more versatile then the other characters, making him in many ways overpowered. Being god and displaying your power every day is definitely possible in some campaigns, and can be considered a design flaw. But I think that is definitely not your role and depends on your play style. Your role should be being Gandalf. Your role is to provide knowledge and digg out your supremacy in desperate situations, making unsolvable problems solvable but better keeping low profile if possible.
I generally play in low magic/heavy role play/heavy story/low combat campaigns leading to this:
In a world of mundanes wizards are mechanically and by flavor the most powerful beings running around (other then monsters). Living in such a world I would fear wizards.
1. If I am mundane and up against a wizard I would either run, or try to trick him (and the npc's often have way better options on observing the party by hiding in the crowd): sneak up on him, try to steal his spellbook, prepare poisoned arrows, attack in closed crowded places, try to get another spellcaster to even the odds (counterspelling and such) ect.
2. If I am a wizard (or powerful intelligent monster) and had some evil plan and hear about a hero wizard shaping the landscape coming for me (or flying circles in the sky on his phantom steed) I would plot against him.
3. If I am a dump but overpowering beater, and get beaten up by the party's fighter I'm no overpowering beater. In this case and the case of powerful magical monsters in open battles a spellcaster is simply needed.
4. If the familiar is stealing the rogues role (too often): the DM should kill it! Who would put his alter ego at such danger anyways (hawk feathers are very decorative after all)?
5. In any way you can assume any wizard would very reluctantly share his power, jealously guarding knowledge of powerful spells, somehow limiting the knowledge of the party wizard.
An extreme example:
In a city based ravenloft campaign I would allow you to take polymorph. You better have a dimension door ready to flee from the angry mob if someone sees you though. And you can bet every secret necromancer you did not know of dwelling in the city will be after your spellbook. You would have to create a new character (not that I did not warn you this is a low magic campaign full of superstitious people hanging elves because they "poisoned the fountains causing the last pestilence").
Another quick thought: Basically transmutation and conjuration are the schools those very powerful spells come from. If I were a wizard or artificer in a high magic world were those spells dominate, I would invent a spell cast as immediate action to counter a single conjuration or transmutation spell of 4th level or lower and sell spell storing items of them.