It is free to use, has many features including GUI, it's easy for new users to learn how to use it without any training required, you can easily customize your tests with its powerful scripting language which makes running loads of different types of test cases very fast.
There are some bugs in the UI that need fixing but other than this I have no complaints about using locust as an automated web stress tester. We run our website under heavy load so we needed something like locust to check if it was able to handle such loads or not.