I believe iojs is not going to be a flop. Look at the current development rate, I would say iojs would replace nodejs eventually if Joyent not doing anything to turn it around.

I prefer to install iojs with nvm instead of the default installer package on iojs’s homepage since it allows me to switch between node version with a single command.

As of current, iojs is basically a dropin replacement for nodejs so you don’t have to worry much.

Install iojs

Install nvm - a node version manager with homebrew

curl https://raw.githubusercontent.com/creationix/nvm/v0.23.2/install.sh | bash

Install iojs with nvm

nvm install iojs

Add these lines to your .zshrc or .bashrc

export NVM_DIR=~/.nvm
source $(brew --prefix nvm)/nvm.sh%

Set iosjs as the default node version

nvm alias default iojs

You can check again with which node to see which version of node is using.