Yes, once you've gone off and created your own package, you're off the upgrade train, and so it's something you ought to take very seriously.
rvm is easier than doing your own packages, certainly, but imagine if you had to use an 'easy', but different tool for everything on your systems.
Also, 'easy' it may be, but I'm not convinced of how things will work out in terms of security, whereas I have a lot of trust in Debian and Ubuntu's security teams. Time will tell, I suppose.
I think the thing here is just a perspective issue. If your focus is the tool, then you want platform agnostic. If your focus is the platform, then you want tool agnostic.
For example, if I'm a ruby developer that ends up using different platforms often (osx, debian, centos) then it's justifiable that I want to use a packaging abstraction that's platform agnostic but ruby specific.
If I'm a primarily a debian user that happens to program in ruby and a dozen other languages then I would prefer a packaging abstraction that's tool agnostic but debian specific.
exactly, you don't want to do them all with a different "easy" tool. For me, I use ruby and rails for sites, and ruby for scripting everything. Basically, ruby is my core tool. I manage my entire system with apt-get except for ruby, where I use rvm. It's worked really well for me.
Or, at work it's basically the same thing but with java and maven to manage java stuff. Java's had a similar history of butting heads with package management systems.
rvm is easier than doing your own packages, certainly, but imagine if you had to use an 'easy', but different tool for everything on your systems.
Also, 'easy' it may be, but I'm not convinced of how things will work out in terms of security, whereas I have a lot of trust in Debian and Ubuntu's security teams. Time will tell, I suppose.