SLF4J is a good replacement for commons-logging or even log4j.
I could be a good idea to migrate.
This represents a bit of an incompatible change from 5.0.5 to 5.0.6, something that could only be accomplished during an alpha stage for the framework.
However, the impact on most user code is invisible.
Where 5.0.5 and earlier injected a org.apache.commons.logging.Log, Tapestry 5.0.6 will inject an org.slf4j.Logger.