Chromes super fast start up speed and clean UI is what caused me to switch when it first came out.
I try to live after the maxim: freedom before convenience (at least in parts of my life).
See: Chrome and Android
But by that measure safari is open source because WebKit is open source.
There's a lot more closed source code in Safari than there's in Chrome. But sure: Why not give them credit for open-sourcing WebKit? Safari is closer to open-source than IE.