Shippable is one of the very few CI servers which support only Docker-based or containerised testing/deployment. So, if you are not in that target demographic, you're out of luck. But if you do use Docker, Shippable packs quite a punch and brings fresh approach to the process. Its not a whole lot customisable, but covers a lot of ground with one-click integration with external services.
Things that I like about Shippable
1. Visual Continuous Delivery Pipelines - Usual method for setting up the flow in most CI servers is to write bash code for all the parts of the process in a single file, but Shippable is totally the opposite. You have a nice timeline-like UI where you can activate different service cartridges like databases, programming languages, notification services, AWS deployment, etc. The whole flow is divided into different parts like CI, CD and notification.
2. Huge range of deployment integrations - Supports direct integration with AWS Elastic Beanstalk (EB), Heroku, Openshift, DigitalOcean and more. Because everything is specified in the pipeline visually, they need to provide deployment adapters for many services and they do a very good job at it.
3. Supports many databases and languages within container - Although docker is nice for running everything separately, its success depends on how modular the images can be made. If a lot of things need to be installed at container startup, it is going to be as slow as traditional VMs. So, most databases and languages are modularised into cartridges you can activate externally.
4. Very affordable pricing even for large organisations - The basic account is free, but parallel testing for many containers or multiple deployments from the same pipeline costs $10 for each extra item. Even after 20 of each, the total price comes to about $400 which is ultra cheap considering the volume of such organisations.
5. Separate pipeline for separate branches in code repositories are supported.
6. SSH login for test debugging is very useful when the bugs are not reproducible in local machines.
The biggest problem is that their available market segment is too small, because Docker is still not that mainstream for testing in most organisations. In its defence, it is very docker-oriented by choice and is quite good for this niche segment.
Other than that, some things I didn't like about it :
1. Very limited support for notification services - Only Hipchat and Slack are supported. Some more like Gitter, Email and IRC support would be nice.
2. Slow test run for basic accounts - Tests for a decent sized project can be very slow if parallel workers are not used.
3. Configuration via both UI (pipelines) and config file is a bit confusing for beginners.
If you are focused on containerised testing, give Shippable a try. It is one of the docker-only CI/CD server that has broken away from standard CI workflow to make it easier for end-users and is very strong with external integrations. It is not much customizable, so if you are a power user this is not for you.
I am deploying some experimental docker-ised backend code to DigitalOcean after some basic testing.
For docker based workflow, Shippable is the best choice at the moment. It is very docker-focused which means it doesnt have to compromise on features which are supported only on Docker, like some other competitors. It was a bit different conceptually from other options I have used earlier, so it took a bit time getting started with, but it is still running smoothly after that setup.