After using cast iron for years, I bought a few de Buyer carbon steel pans and I love them. They're thinner and lighter than cast iron. They're more responsive to temperature. They season better than cast iron and are incredibly non-stick. They might be a bit more sensitive when it comes to care than cast iron though, and are certainly a lot more expensive.

I still use my cast iron cookware for times it is appropriate, but highly recommend carbon steel as well.