I voted steam, knowing that there are several steam sourcebooks on or coming to the market at present. But I'm not thrilled with what I've seen so far. Rules are important, but they should be the means of integrating a steamtech/punk feel into the game. But just putting steam in D&D does not make steampunk. It makes Dragonsteam. And I don't want Dragonsteam.
I guess what I'm saying I'd like to see is a high-quality "Steam d20." Something with a substantive setting and the rules to support it. Something with its own flavor, it's own discovery. Its own ecologies and societies and cosmologies.
At ENWorld Boston I played in a game called Septentrionalis, which is a d20 colonial setting. The rules were just an extension of the d20 system we know and love. But the real beauty was in how the rules just felt like they were just there to facilitate the setting. The whole package is what works. It's not just a paste-in to D&D.