Kristof,
I don't know of a way to regularize the Verbose GC output from JRockit. While I was working at G-Log, we had to modify our GC graphing scripts to specifically map against JRockit's output. In fact, we had to do the same for the IBM JDK. One option may be a Perl or Ruby script to convert the GC info into a Sun JDK format.
The best option I've found, so far, has been BEA's management tools, including the JRockit Console and Mission Control.
Just for reference, I've found the following tools useful for diagnosing JVM memory issues with the Sun JDK, though I don't know if any are compatible with JRockit:
BTW, the best CPUs I've seen in use with OTM and other Java application servers are the Intel 5160 and E5355 CPUs.
Hope this helps!
--Chris