MALLET has a full suite of helpful tools, but I primarily use it for topic modelling. I love the ability to scan multiple documents at once using MALLET's Topic Modelling Tool. It allows me to vary how many words appear together and which words to leave out. It works quickly and efficiently, allowing me to play with the variables to look at different outcomes.
MALLET is not intuitive. Their tools are really useful, but you may need a thorough tutorial on how to use them appropriately before diving in.
I have used MALLET to analyze responses to faculty surveys and conduct topic modeling on research projects. I have found the Topic Modelling tool to be particularly effective at providing initial analysis categories to give me a sense of what to look for.