and they are much freer to do absurd things
cuz Summons have limitations
planar ally is Cleric, planar binding is sor/wiz, gate is both
for a druid specifically, summoning is definitely up there
but the druid's real strength is his "everything" ness
he's got summons out the wazoo, not to mention the AC he starts all combats with
he's a terrifying melee warrior himself