It's important to have at least 2 healthy browsers (in market share). They keep each other honest, if I might put it so tersely. We all remember IE6, and were in danger territory again with the current percentages.
For this reason, personally, Chrome would have to be 2x or more better than Firefox for me to consider switching to it. Do what you can to keep the market diverse.
If the percentages were reversed, I'd absolutely be running Chromium or a variant.