In our environment compressing log files does not work correctly.
As example here is the logger configuration:

<appender name="rdf-api-debug-file-appender" class="ch.qos.logback.core.rolling.RollingFileAppender">
<append>true</append>
<filter class="ch.qos.logback.classic.filter.ThresholdFilter">
<level>debug</level>
</filter>
<rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
<fileNamePattern>D:/Temp/rdf-files/logs/%d

/debug/rdf-api-debug.log.gz</fileNamePattern>
</rollingPolicy>
<layout class="ch.qos.logback.classic.PatternLayout">
<pattern>%date,%-5level,%logger,%thread,%message%n</pattern>
</layout>
</appender>

At Nov, 5th I see a directory "D:/Temp/rdf-files/logs/2008-11-04/debug" with the following files (and time of last modifucation):
rdf-api-debug.log, November 05, 2008, 12:12:26 AM
rdf-api-debug.log855980476945031.tmp, November 05, 2008, 12:11:52 AM
rdf-api-debug.log856014875320881.tmp, November 05, 2008, 12:12:26 AM
rdf-api-debug.log.gz, November 05, 2008, 12:11:53 AM

The first three files and the log file in the .gz-archive have all the same size.
So compression works, but the original log file and the temporary files are not deleted.

Our application uses several threads, perhaps this causes the problem.