I have played a mage who only uses stat-buffs and wizard eye and similar, non-flashy spells. It's actually extremely effective. While a fireball certainly can kill a bunch of stuff, giving the fighter a big bonus to his Strength can often increase damage output for the whole party much more efficiently (especially in 3e).
I also really loved wizard eye. I could scout out a good chunk of a ruin before we even set foot in it, which helped us a lot (and frustrated the heck out of the DM). This helps mitigate the 15-minute workday problem a bit, since the scouting will be useful for the entire day, and only take up one spell slot.
I recommend those of you who like mages consider trying this out for a session, just to see how different, yet very effective, it is.