I have seen some issues with the BOINC client not keeping proper cpu time on the clean energy project as these are large work units that have lots of I/O that is not counted. Even on a dedicated cruncher it results in large differences between cpu time and wall clock time. This gets worse when you try and run 4 or more work units. I hope that was one of the issues WCG was trying to resolve. I mostly use the apt-get version in Ubuntu.