I say go for it. I've been using it for about 2 years, and I no longer feel like distro-hopping (not sure if you fall into that category of Linux user), because it's not opinionated about how it's meant to be used. It gives you all the tools (and foot-guns) to do whatever you want with your computer.

You don't need separate computers for a local mirror and/or build server to run Gentoo, I've never done that. I've never owned a Mac, so I can't really offer any tips hardware-wise, but use a live USB of a distro that you're already familiar with, so you can refer to the handbook as you go. The people on Gentoo's IRC channel & forums are very helpful if you come against any roadblocks.

It does take a while, not gonna gloss over that. Once you have it installed, there are very few issues that would require a full re-install. Portage is an awesome package manager, the language of its warnings/errors took some time to wrap my brain around, but it's very verbose in describing what's going on.