We are gearing up to do some profiling/performance improvement at work, and we use MacPorts (mostly at my stubborn insistence) to install Ruby on our OS X dev boxes. Unfortunately, the MacPorts version of Ruby is not DTrace-enabled, so we were faced with the decision to either go with the Apple-installed Ruby or not use DTrace.
Fortunately, there was a third option. I spent some time massaging Joyent’s Ruby DTrace patch so that it would compile with Apple’s version of DTrace (subtly different from Solaris’s), and so it would play nice with the other patches in the official Ruby MacPort distribution. Anyway, long story short: you can get it via my newest RubyForge project, rubyport-dtrace. You can install either from the tarfile or by checking out from Subversion, see the instructions in the distribution.
Why I like MacPorts: I like being able to cleanly remove software I install. I also like that I can compile Ruby with DTrace and other patches that I might want (such as the Railsbench GC patch, which I’m also working in to the rubyport-dtrace (dare I call it) code, it might already work but I haven’t tested it).