Ranked in these QuestionsQuestion Ranking
Pro Large community
Puppet is very mature and relatively old. This means that it has gathered quite a following over the years. This large community means that there are a lot of modules, guides and configuration recipes ready to use built by the community.
Pro Declarative sematic
You define the state the server should be in and Puppet transforms it that state. This is opposed to explicitly declaring a list of actions to be performed.
If a developer wants more flexibility and control there's always the option of falling back to explicitly running commands but that's discouraged.
Pro Broad cross-platform support
Puppet is a complete solution in terms of available features and modules. It has full support for all the main Operating Systems and provides lots of tools for its users.
Pro Easy to learn
Puppet is model-driven and easier for diverse teams (that may include non-devs) to learn than it's main competitor, Chef.
Pro Helpful UI
Puppet's UI is very useful. It allows real-time control of managed nodes by using modules and configuration recipes that are on the master servers. Although the UI is great for management, it lacks when trying to configure modules.
Con Interaction between modules can get quite complex very fast
Due to it's out of order execution you can easily get into race condition between different modules. You have to be very careful declaring pre-requisites for the tasks so they don't step on top of each other. On the other hand when you get this lets you deploy things much faster than straight line execution tools
Con Solid knowledge of Ruby is needed to create your own modules
Modules and configurations are written in a specific language based on Ruby or in Ruby itself. So in order to be able to create custom configuration and modules you need a solid knowledge of Ruby.
Although it's fair to mention that there are many modules already available for every use-case.
Con Lacks flexibility
The lack of control over Puppet's model-driven approach can result in less flexibility and power from the tool.