Freeze is very similar to Ice Spike and Icy Spear in operation, though at a lower cost than either of them. It does less damage as well, but slows targets for much longer. This makes it ideally suited for tougher opponents (who won't be dead in 3 seconds). Cast it once at the start of a fight and then use other means to actually kill them. Like Ignite, you must have Ahzidal's Ring of Arcana equipped in order to use it.
Like most Frost spells, it can be used to set off Frost Runes from a safe distance.
Freeze spikes which hit enemies will continue to exist after they die until you leave the area. This makes the corpses easy to spot from a distance for looting.