Pro Easy to try out new services without requiring any changes to your page code
Segment integrations can be setup with configuration only requiring zero code deploys on your server. There is a fast turnaround time for adding the integrations that gets the new service on your site in minutes, making it very quick and easy to try out a new service while you're evaluating whether to use it. Since the scripts are loaded dynamically, it allows you to deploy new services with zero html changes so you don't have to break page caching.
Pro Provides a single simple and consistent API for all integrations
Segment.io's api is very easy to use, with very straightforward methods, like
Page, and each API call is hooked up to your chosen service integrations to call the equivalent method so you only need to learn one API.
Pro Buffers your data playback for service integration downtime
All your historic data is stored in backup logs, and Segment.io will automatically replay your data for you to all your integrations during service interruptions like scheduled maintenance. With a business plan (requires inquiry), you can replay historic data to back fill events if you want to add a new integration, meaning your data is completely portable and can be taken with you from service to service.
Pro Libraries in multiple languages
Official libraries exist in the following languages and platforms for server side tracking:
All their libraries are open source, so you can follow their lead if you need to port one to an unsupported language.