It's somewhat similar, but the main difference is that Ohm has a strict separation between syntax and semantics. We think this has several benefits, which we describe a bit here: https://github.com/harc/ohm/blob/master/doc/philosophy.md

Another difference is that Ohm grammars can contain left recursion -- both direct and indirect. IMHO this is a pretty big deal, but I know that some people don't agree, and think that avoiding left recursion is not a big problem.