It is very helpful for me as I am developing an android app which requires push notifications from server side with pusher library.
The best thing about this service provider it provides free trail period of 30 days after using their services we have no any issues in our project development process. There should be some other options like they provide more security keys or something else if there's nothing good then why not give them try because its totally FREE! Push notification feature helped us develop my Android application much faster than before without paying anything extra.