Jenkins has done a great job in getting continuous integration as a workflow into the hands of many developers.

But their usability is completely out of date and their current user base doesn't let them evolve to where they would need to be. Especially integration with PaaS services like Heroku should just be there from the start, but has never been a focus for the Jenkins community which still seems to be very on-premise based with all of their infrastructure.

More and more developers seem to be jumping on hosted solutions now (e.g. https://www.codeship.io where I am one of the founders)