Without a single line of code, that is not even knowing what the script editor looks like, you can go very, very far, but you have to be aware of two things. You will still need to learn and master playmaker, in order to go very far with it at all. this goes without saying of course, but sometimes we forget when we see a new tool that looks cool, that mastering it will be key to success.
The problem might be elsewhere for Joe, if he doesn't have any experience in 3d and virtual 3d, it will be difficult to pick up , because he will have to learn 3 things at once, what is a 3d world and what it means, Unity itself and playmaker, so this is something to be very careful with, it's not because playmaker requires no scripting, that it means you don't need to know what a virtual 3d world is , what a collider is, what you can do with vector maths, or how to animate a model.
Having said that, I know how to script, I know what real time 3d is, and will never start a new project without playmaker! simply because not only you can do a lot without scripting, BUT it gives you access to a lot more than that. It's simply easier to performs some tasks with playmaker than with scripts! I have for example designed a full blown robot simulator for industrial application, and without playmaker it would have been hell, with playmaker it all of sudden becomes fun and really comprehensive. I do mix scripting and playmaker together tho, because I am no afraid to and because sometimes it is easier to do thing in script, especially for advanced frameworks and tasks,like Inverse Kinematics or really complex management of data, or simply because you will use a totally cool framework but you will need to tight it with playmaker, so some binding scripts or special actions will be required.
To get a feel, I strongly encourage you to simply sit down with a cup of your favorite drink and watch all the videos and screencast available, this will certainly give you a good grasp of what it can do.
Not going that "far" in terms of what playmaker can do, I ported M2H great c# simple games examples, I suggest you get them from the app store, and then study the help I am currently building around it, 100% playmaker, not scripting AT ALL for them games, I made them with the standard set of playmaker action, nothing more: https://hutonggames.fogbugz.com/default.asp?W880
and for of them game, it took me less than an hour to do them! that opening the game, removing all scripts and build the interaction from scratch with playmaker!
AND, if you ever find your self stuck with a process you have difficulty to create, simply ask us, we will happily help you, and even create these actions that you might need, if you don't really feel up to create your own ( which is by the way very, very easy anyway, and the forum is loaded with examples of custom actions, as well as simply opening the standard set of actions ( all playmaker actions are open source, so you can really learn from it).