If it's just you, doing stuff for yourself, RVM may not bring a lot of new to you: Correct.
RVM is great to test against different versions (and implementations), especially if you do a lot of team-work: For instance, if you work in a team, or in production environments, the newest version of Ruby may be ahead of the production version, and then it's a must being able to switch from one version, or implementation, to another--painlessly.
A personal use case I could come up with (there are a lot of them): You make an app., and it runs with Ruby 1.9.2. You deploy this app., and then Ruby 1.9.3 is released, and your app. is no longer compatible. You want to stay on the cutting-edge still, so you want 1.9.3, but your project is not compatible with 1.9.3, and still needs some work to be, since it's grown rather huge. Here RVM would be handy!
When I was just toying around with Ruby, I didn't use RVM either. It's not until I've got work within the Ruby field, I've had the need for it. :)
RVM is great to test against different versions (and implementations), especially if you do a lot of team-work: For instance, if you work in a team, or in production environments, the newest version of Ruby may be ahead of the production version, and then it's a must being able to switch from one version, or implementation, to another--painlessly.
A personal use case I could come up with (there are a lot of them): You make an app., and it runs with Ruby 1.9.2. You deploy this app., and then Ruby 1.9.3 is released, and your app. is no longer compatible. You want to stay on the cutting-edge still, so you want 1.9.3, but your project is not compatible with 1.9.3, and still needs some work to be, since it's grown rather huge. Here RVM would be handy!
When I was just toying around with Ruby, I didn't use RVM either. It's not until I've got work within the Ruby field, I've had the need for it. :)