I try to use 5.4 when I have the choice. I use Ubuntu on my VPSes, and a lot of providers' Ubuntu image is 12.04, which only has PHP 5.3, so I use a PPA to get 5.4. I like it a lot (and thus don't mind going through the above hoops) because of two main new features: function return array dereferencing and short array notation. I'm used to both of these from JavaScript, so it's great having them in PHP.