The best thing is AWS C9 is online, i don't need to install anything, and it support the most used languages, as C, Java, PHP, Python, etc. I can code from my mobil, tablet, pc, from anywhere, and i can share my code live with my co-work team, and we can code at the same time thats just amazing only need update the website to see the changes and run the app/website, also it help to write code faster with shortcuts, can create files, delete, change, create folder, is so powerful. One of the best thing is also how i can still using key shortcuts to save file, or save all as i do on my pc, i can upload or download complete projects and use on my desktop/laptop with one click and it is already compresed. It can be free but also, can be slow, but you can upgrade the EC2 PC to increase the performance.
The only thing what i dislike is there isn't a key shortcut to run the app, is annoying to move the mouse only to click on RUN to compile the project. It can be free but also, can be slow depends of the project, but upgrading the EC2 pc it can be solved.
There is a free tier, which is more than enough for small projects, use it, test it, is very powerful tool, if you feel it is slow to compile, just upgrade your EC2 PC. Use it to do remote team work, for web development, app, software. AWS C9 work perfect with others AWS tools, like AWS Commit, Lambda, you can do big projects with them.
It let me to write code from anywhere, and i dont have to be always with my laptop, or need to install any other IDE, and save all the problems which can happen when installing them. Is so helpful for SCRUM projects, it let work more than one people from remote location at the same time, with the same code thats is wonderful.