Is that instruction set available?

Yes, it's the standard Webassembly instruction set

What are gas fees looking like?

No gas fees, but there will be an RC system in the future for lite accounts using staked HBD

Is there "revert" functionality when things go awry?

Yes, contracts can revert execution and fail the transaction if required conditions are not met. We are still working on this functionality and the exact specifics but it will be available in the near future.

What is most different than say, a solidity(ish) setup?

VSC smart contracts can written in any webassembly compatible programming language. Starting with Assemblyscript to Rust/golang in the future. A lot is similar in terms of expectations and semantics. If you have any specific questions that would be a more helpful comparison and breakdown of the two technologies.