There are many choices of cloud development environment. Many emphasize on collaboration. For me, collaboration is easier throught some other tools such as git and slack. Thus, all I need is a machine which I can login with SSH. The IDE provided by cloud development environment usually do not suit me. Nitrous and Koding both provide SSH login at free plan.
I initially use Nitrous and earn some free N2O. So the total N2O is 235. It gives either a machine of 512MB/3.75G or 640MB/1.75G. 512MB is barely enough and I cannot have both Rails server and test at the same time. The machine is a little bit slow depending on the time of day. And from time to time, the restarting will hang. So I decide to give Koding a try.
Koding provides free 1G/3G plan, which is better than Nitrous. It gives a virtual machine to start with. Therefore, there are more freedom to do whatever you want, but unlike Nitrous, I have to set up many small things by myself. Nitrous indeed provides what it claim: "Claim your Ruby Development Box in 60 seconds". I spent half a day to get PostgreSQL working on Koding since I am not familiar with its configuration. But I can use rvm on Koding while there is not enough resources to do so on Nitrous. And Koding feels faster.
Koding is not flawless. First, it takes longer to boot up than Nitrous. If you only need to boot up once per day, it will be fine. Unfortunately, it will automatically turn off after 1-hour inactivity. And from time to time, I will be forced to log out because it thought I were not using it while I was actually doing something. The activity detection of Koding is not very good. So remember to save your files more frequently. And it use dynamics IP for its virtual machine (domain name is fixed) and sometimes I cannot connect to it due to DNS problem.
So now, I keep both of them but spent more time on Koding for a Rails application development. If Koding kicks me out too often, I might have to go back to Nitrous.