OK, yes I love Unix, no I don't know how to compile stuff with make. yes I've used make, no it isn't my favorite tool. yes I like getting my hands dirty, no I don't want to spend all day configuring a Unix box, even a Mac OS X Unix box, pretty though it is.
If you need to get Rails up and running on OS X, get Darwinports. It is fast, it is nice, and it is easy. A client told me I needed Locomotive, and Locomotive is great, but it doesn't seem to ship with Edge Rails, and it doesn't get you around the fact that Ruby's on v1.8.5 and OS X is still shipping v1.8.2, without gems.
Also, Rails has this gigantic community, this huge hype machine, and it's an incredible piece of technology to boot. But guess what? You want to get Seaside up and running on Mac OS X? You do two things. You install Squeak (one click) and then you install Seaside (another click). Then you're done. I realize some of that is due to the differences between Ruby and Smalltalk, but still. Seaside definitely clobbers Rails on ease of install. Not the most important factor in every analysis, but certainly the most important factor on a lazy Sunday afternoon when you're still half-asleep.