As a player, I've used crowd control as a wizard and made good use of the wizard when I'm a mundane.
As a DM, I've had crowd control spells destroy "overpowering" encounters.
I've also seen our entire party teleport-ganked by a rival adventuring party. You don't realize how devastating Forcecage, Solid Fog, Cloudkill, Rock to Mud, and Mud to Rock can be until they're used to lock down your entire party in one turn.
Having seen crowd control from all angles, I can say that it adds a tactical element to the game that is entirely necessary for it to be fun.
If anyone cares about the above encounter:
[spoiler]
Our 12th lvl Party: Elan Psion (Egoist), Goliath Barbarian/Fighter (Dungeoncrasher), Gnome Artificer, Warforged Dragonfire Adept/Crusader, Aasimar Monk/Ur-Priest
Enemy 13th lvl Party: Gray Elf Wizard/Iot7V, Gnome Beguiler/StP Erudite/Cerebremancer, Human Hellfire Warlock, Dwarf Monk/Ardent
Pre-combat: Enemy Teleports all around us, buffed to the gills
Surprise Round: (Wizard, Beguiler, and Warlock all use readied actions, then take their surprise round as normal)
-Wizard casts Forcecage and Cloudkill on the Fighter, casts Solid Fog to separate the DFA from the rest of the party
-Beguiler casts Split Ray of Stupidity on the Psion and Artificer, Wall of Ectoplasm trapping the DFA, and Quickened Entangling Ectoplasm on the Ur-Priest
-Warlock casts Nightmares Made Real over the party and Chilling Tentacles over the Artificer and Psion
-Ardent casts Astral Construct and Quickened Ego Whip on the Psion
Summary: Before the first round, we were screwed. The Psion and Artificer lost access to their high level spells/powers, 3 of us were either entangled or grappled, the DFA was cut off from everyone, the Psion was dazed, and the Fighter was stuck in a Forcecage/Cloudkill. And we had to fight 4 high-level enemies who had prebuffed, summoned, AND had concealment (we saved vs NMR).
We actually managed to come out on top because the Artificer managed to dispel the Solid Fog blocking the DFA with a wand and used a scroll of Disintegrate on the Fighter's Forcecage. The enemy tried to Rock to Mud/Mud to Rock under the Ubercharger, but a second scroll of disintegrate fixed that. One Pouncing Heedless Charge later and the enemy was down 1 Wizard. The Psion managed to break free from his daze and after a pair of augmented Mind Thrusts, the Ardent was down. The warlock was tough to bring down, but a well-placed Harm by the Ur-Priest brought him to 1hp, followed by another Mind Thrust. The Fighter then proceeded to smash the Beguiler into his own Wall of Ectoplasm for heavy Dungeoncrasher damage. We had two guys in the negatives by the end of the fight, and had no spells left. We had to end our adventuring day right then and there. It was awesome
[/spoiler]