Jake,
An aluminum sprocket is plenty hard enough to use.
Only when a chain has lengthened in pitch past 1.5% of new, will it start to deform the teeth. I don't care what some psuedo experts will tell you...brute force of the bike will NOT deform the teeth.
What happens when you run a steel sprocket is that youu get real comfortable with your drive set-up because you see nothing happening to the teeth. They are "too" hard to be deformed by the growth of pitch of the chain.
Consequently, when the chain does grow, the hard sprocket that fights the deforming of the tooth actually starts to accelerate the wear and pitch growth of the chain. So the chain gets ALL of the wear. This allows you to run the set-up until the chain is wayyy past where it should have been changed out, even to a point of endangering the rider.
Anytime you hear a guy say his chains are all crap but his sprockets are holding up just fine, prolly is going through this.
Keep an eye on your chain and replace it once it gets to about 1-1.5% growth and you will see good long service from an aluminum sprocket.
Running an aluminum sprocket gives you a quick visual of where your drive set-up is. Especially if you aren't one to measure and know where your chain is.