I went through the MOOC material and tried it out for a few small things. It inherited a lot of the unique Smalltalk features which make it sort of alienating to a modern programmer. For instance, all your code resides in an image file, and if you want a copy of your code the environment does some extra epicycles to copy it outside. The choice to make everything a message, including basic flow control takes some getting used to. As you just sort of hack your image to do what you want, it just sort of turns into a ball of mud. The paradigm they're going for is TDD for everything. Personally, I feel this is a big step backwards from most mainstream scripting languages adding on type annotations. It's not easy to use a simple text editor. You pretty much have to use their integrated environment.

Then, there were a few problems that were specific to Pharo. Pharo went through a couple different package systems and the different package systems don't necessarily have the same packages. Pharo has had major breaking changes in their GUI toolkit, so if you found a package that did exactly what you wanted and were able to install it, it just wouldn't work.