I'm currently playing a conjurer in an Eberron game, and I gave up Illusion and Enchantment. It's rough giving up both Will save-inducing schools (and Power Word, Kill), but I enjoy my blasting spells and have an unholy love for necromancy. As has been previously mentioned, Spell Focus: Conjuration is a bit of a waste at low levels, but is well worth it for Augment Summoning alone. I currently possess 6 spells for which that feat is useful (Summon Monster I,III, Summon Undead I-III, Summon Swarm), and it seems to help a great deal. An augmented skeletal dire wolf is a thing of beauty, if you don't mind casting [Evil] spells.