I too feel mcmmo will make the game significantly easier, too easy, even-- that's what the creative server is for.
If made appropriately difficult, I could see it becoming a "maybe", but even then it only serves to increase the disparity between players. However, I don't think it should be enabled in any way, shape, or form until it is fully and properly configured for our needs.
It was my understanding that the whole point of the new world on the dev server was so that that would be the rpg world, and the main world would be left alone as a standard building world. While this still wouldn't help the economy, it would allow players that don't wish to participate in the rpg aspects have a place where they don't have to deal with other players having perks which grant unfair advantages.
I have to agree with Slurth that for the uninitiated, mcmmo (or any RPG plugin, for that matter), is extremely confusing. Minetown was my first non-vanilla server, and even with the limited plugins we have, I found it very confusing. I can't imagine how overwhelming it would have been to learn an RPG system on top of the quirks already implemented by various plugins.
I personally think we should continue with what I thought the original plan was-- leave the main server alone, and when we bring up the second world, let that be the RPG world. Something that has been gone over and carefully balanced and tuned, something that players can engage on their own terms and choose to participate in when they are ready.