Console debugging is done by first enabling debug messages. In v2.0 of the engine it's:
R.Engine.setDebugLevel(2);
Then you can log stuff to the console with:
R.debug.Console.debug("Hello World!");
There are a few different debug-level options with 0 being the most info, and 4 being errors only. Level 2 is debug, warnings, and errors. Setting it to -1 will turn off all debug messages. The engine automatically detects which consoleref to use based on the browser. You do not need to create an instance of the consoleref to get debugging. If you are in Firefox, just open Firebug and you'll get debug messages after setting the appropriate debug-level.