I am typing fluently this using the Colemak layout and I can switch easily to Qwerty. Colemak is the easiest/fastest layout for me. It is like driving stick vs automatic, I can change whenever I want without thinking about it. I also tried Dvorak. However, shortcuts like CTRL+C were not possible with one hand anymore. This was a no go.

The hardest part of learning a keyboard layout is the first week. During this week you cannot type on the autopilot at all (even my qwerty skills were fucked up).

I recommend starting learning a new layout during a holiday because it will break your productivity. For training, you can use http://klavaro.sourceforge.net/en/index.html, which has support for Colemak.

After 4 weeks of typing more than one hour per day, I managed to hit the 50 WPM at Colemak. It is also important to type 30 minutes per day using qwerty during this 4 weeks so that you will not lose your qwerty skills.