RVM is great for some things and a bane for others. Like you, I use it all day, every day to build & test multiple Ruby projects on my MacBook. It has really increased my output and reduced my hair-pulling.
On the other hand, automating and managing a server install using RVM is a nightmare. I don't want/need compilers on my servers, I just want to push a package out and have it work (i.e. APT).
out of curiosity, what other issues does RVM pose to "others", other than having to apt-get install compilers?
also, wouldn't you need compilers anyway, for a whole lot of gems that use native extensions?
No, that is the beauty of using system packages, you just apt-get install them (if they are packaged, that is). That is why it is so important for projects to make it easy for distributions to (re)package extensions.
2. Easy to run an app which requires an older version of ruby (I typically use 1.9.2).
Advanced features like gemsets allow finer grained control but only if needed.