I'm a level 50 Enchanter on the Time-Locked Progression server and I felt that the negative feedback on this spell is 100% incorrect. I'm not sure on the history of the Spin-stun but I think this spell was at one time nerfed and now was again revamped when they gave the updated high-level spell line back to enchanters at ~75. If your an Enchanter, and you're fighting mobs level 55 or lower this should ALWAYS be on your spell bar.
This spell is a plain and simple single target stun. It works on creatures up to level 55, like the first 4 of our PBAoE color stuns. It's the most effective stun in the game for several reasons. The first being its duration. With spell haste 1 you can STUN LOCK a mob completely, with just this spell. Without spell haste 1, the mob will squeeze one combat round off before getting hit with the stun again. This stun also runs off Alteration, which for a classic era enchanter is the best choice for specialization. Once a chanter is in their mid 30's, assuming they have a group with good DPS, this spell will replace the need for slow completely.
Situations when this spell is most effective:
Charm breaks
Caster mobs (complete lock down for ones with dangerous spells)
Group member pulls agro
Tank is AFK, slow to react on pulls or has trouble holding agro
Soloing using your weaker summoned/charmed pet to beat much harder mobs by chain stunning its foe.
Enchanter Tank - Anyone can tank when they aren't taking damage.
You can spin-stun a mezzed mob before the tank goes to break it if they don't always wait for successful taunts.
Anyways, this great spell deserved a positive post.