Disclaimer: I am the founder of log4j, slf4j and logback projects but unaffiliated with log4j 2.0.
As I understand it, notwithstanding its name, log4j 2.0 is very different than log4j 1.x. As far as the user API is concerned, log4j 2.0 is largely incompatible with log4j 1.x. Log4j 2.0 provides an adaptation layer for log4j 1.x which at present time (2012-08) is undocumented.