JCL 1.1.1 has some minor additions in comparison with the currently supported 1.0.4. The CLIRR report for the API is:
INFO: 6000: org.apache.commons.logging.LogFactory: Added public field
DIAGNOSTICS_DEST_PROPERTY
INFO: 6000: org.apache.commons.logging.LogFactory: Added public field
HASHTABLE_IMPLEMENTATION_PROPERTY
INFO: 6000: org.apache.commons.logging.LogFactory: Added public field
PRIORITY_KEY
INFO: 6000: org.apache.commons.logging.LogFactory: Added public field TCCL_KEY
INFO: 6000: org.apache.commons.logging.LogFactory: Added protected
field nullClassLoaderFactory
INFO: 7011: org.apache.commons.logging.LogFactory: Method 'protected
java.lang.Object createFactory(java.lang.String,
java.lang.ClassLoader)' has been added
INFO: 7011: org.apache.commons.logging.LogFactory: Method 'protected
java.lang.ClassLoader directGetContextClassLoader()' has been added
INFO: 7011: org.apache.commons.logging.LogFactory: Method 'protected
java.lang.ClassLoader getClassLoader(java.lang.Class)' has been added
INFO: 7011: org.apache.commons.logging.LogFactory: Method 'protected
boolean isDiagnosticsEnabled()' has been added
INFO: 7011: org.apache.commons.logging.LogFactory: Method 'protected
void logRawDiagnostic(java.lang.String)' has been added
INFO: 7011: org.apache.commons.logging.LogFactory: Method 'protected
org.apache.commons.logging.LogFactory newFactory(java.lang.String,
java.lang.ClassLoader, java.lang.ClassLoader)' has been added
INFO: 7011: org.apache.commons.logging.LogFactory: Method 'public
java.lang.String objectId(java.lang.Object)' has been added

Since many libraries claim a dependence on JCL 1.1.1, having SLF4J support it would be beneficial.