You've been burned by Juju? I am curious, since it looks like it was a bit of a not-invented here GUI to facilitate things people would do with configuration management, without doing it like configuration management or even like packages.
juju isn't really config management.. its orchestration, and its been around since before that was cool (4yrs). thankfully orchestration is in revival mode as the hot thing in devops is containers which obviate a good portion of the install side of config management, and leaving discovery, provisioning, resource management, etc around.
maas is standalone.. and is pretty cool imo, as a an api for controlling baremetal machines (ipmi, libvirt, pxe, etc) with cross os support and used on everything from super computers to intel nucs.
It's a lot more than configuration management. It's coordinating multiple machines across a cloud (public or private) - we call it "orchestration". It's not just "install this software on this machine", but "install this service (may be multiple packages of software) on N machines that are dynamically allocated from the cloud, hook it up dynamically to this other service on M other machines, and scale it all up and down." All with just a few trivial commands from the user. The GUI is just a tiny piece that tries to communicate the enormity of what Juju is doing behind the scenes.
With a few drag and drops on the GUI or a few commands on the CLI, you can deploy an entire openstack onto your hardware in minutes instead of hours or days. You can configure a highly available web front end, connect it to a highly available database cluster, with log collection and monitoring... again, this is something you can set up in minutes, not days.
Juju uses puppet and chef etc to configure machines - that's what those tools are good at. But Juju is at a higher level - connecting the machines together into services, and connecting the services together into an application.
Here's a post about deploying a fully functional Hortonworks Hadoop cluster in less time than it takes to go to get a cup of coffee at the local coffee shop: http://www.bigdatachat.net/when-amir-met-juju/
