they have to be at range for the slow to mean anything
This is incorrect.
The slow part is automatic for 1 round. This means for 1 round EVERY enemy in the area is slowed. Imagine a scenario where 4 creatures are locked in melee with a fighter and rogue (not an uncommon scenario in 4e). The creatures attack and badly damage both of them. The wizard (the warrior and rogue just delay if they're before the wizard) casts sleep. All 4 of the enemy melee combatants are GUARANTEED to be slowed. Now the injured fighter and rogue are up. The fighter and rogue shift out of melee with their move action and move 5 (or 6) squares with their standard action. The cleric and paladin safely heal the fighter and rogue. The enemy is now up and our combatants are 6 or 7 squares away. The enemy uses all their actions to move 4 squares -- they're now STILL not in range to attack and on average 1 falls asleep and 1 is still slowed. The cleric and paladin can heal again or not as necessary. With 1 daily, the party has taken 1 combatant out of the fight (or created a helpless target, which can't be good for that enemy) and given two "free" heals. That's nice.
Here's some more useful juju -- the rogue is attacking a slowed target. He uses Positioning Strike (level 1 encounter power) to do damage and slide the creature back 3 squares. With his move action, he then backs up 2 or 3 more. On the creature's turn, even double moving, it can't reach him -- the rogue just gained what amounts to a free attack.
Slow is useful if you use it tactically to your advantage and is also very nice in combination with other powers -- especially rogue and ranged combatant powers.
So, it's good at range if there are ranged attackers, it's good even close up if you use it tactically. It's a GREAT control spell - it gives you real control of the melee battle field for at least one round, and that can easily turn the tide.
So, how is it compared to other level 1 dailies?
Wizard Daily: Sleep = battlefield control for at least 1 round allowing an extra round of healing, repositioning, and potentially free strikes PLUS an average of 1 opponent being rendered helpless when used on groups of 3+.
Cleric Daily: CoL = 3[W] against one creature and an average of +7.5 damage over the next two rounds. Minimum it guarantees 1.5x weapon damage.
Fighter Daily: BS = guaranteed 3[W]
Paladin Daily: OPoD = 3[W] against 1 creature + an average of 1.5d8 over two rounds. Minimum guarantees half that.
Ranger Daily: SpT = 2[W] versus 2 creatures with better than average chance to hit.
Warlord Daily: PtF = 3[W] + target can't shift if two of you are adjacent.
Warlord Daily: WRO = 3[W] + slide an ally 1 when you and your friends hit.
Warlock Daily: CotDD = 3d8 + slide enemy 3 squares, sustain minor to keep sliding that target 1 each round.
Basically, the others average (fighters are usually a bit higher) 3d8+ability vs one creature and you can either move it a bit or move yourself a bit. Personally, guaranteed control of enemy positions for 1 round giving me the ability to safely heal and reengage as I desire, plus the average of taking 1 guy out of the fight entirely for a couple rounds, is FAR better to me than an average of 16 (or 22 in some cases) damage (average of 3d8+4 - assuming you even hit) to ONE guy and controlling his movements a bit.