My current road bike is steel and my next road bike is going to be steel. Having said that, I have heard (and it makes sense to me) that on good bikes ($1000+), the geometry and construction have more to do with how stiff/harsh a bike's ride is than the material.

Aluminum is actually a more compliant metal--that's why the tubes are always bigger. But I think a lot of cheep aluminum road bikes (<$1000) have poor design and so ride badly. It's like comparing a $200 steel frame mountain bike that weights 40lbs to a good tapered $1000+ steel frame bike. It's not the same beast.

I'd wager that manufactures design aluminum bikes to be more rigid because that's what people expect. Also, the fork and wheels are going to have a lot to do with how harsh the ride is. Even the tire pressure for chistsakes makes a big difference. I think a lot of the "harsh" talk is only subjectively perceived differences due to preconceived expectations. It's very difficult to do an objective test. I think the only thing to do is test ride a couple of bikes and pick the cheapest one that feels good to you.

If you're looking in the $1200 price range take a look at the Jamis Quest and the LeMond Alp D'Huez (sp?). There're both steel, around 20lbs with carbon forks and 105 components. Those are the two I'm trying to decide between, and they seem like awesome bikes for the money.