Om will also always have limited reach because it uses Clojurescript. I know that some people love it but I personally don't, and if nothing else it is an extra barrier for entry that some just won't get past.
Not really. It's basically just a means of using ClojureScript with React. That comes with some great stuff (immutability, for one), but AFAIK it doesn't change anything too dramatically.
It completely changes the way you think about modelling applications and their events. It's closer to Flux on steroids rather than a thin wrapper on top of React.