Same program stack trace with Xmixed and Xcomp looks differently:
(the difference is that "- waiting on <0x0000" is missing in the second case)

2010-07-08 15:08:23
Full thread dump Java HotSpot(TM) 64-Bit Server VM (17.0-b16 mixed mode):

"scenario2" prio=10 tid=0x000000004c631800 nid=0x1f24 in Object.wait() [0x00000000424b0000]
   java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
- waiting on <0x00002aaadcc67008> (a java.lang.Object)
at java.lang.Object.wait(Object.java:485)
at tmtools.jstack.share.debuggee.WaitNotifyDebuggee$WaitThread.run(WaitNotifyDebuggee.java:23)
- locked <0x00002aaadcc67008> (a java.lang.Object)

===============

2010-07-08 15:08:52
Full thread dump Java HotSpot(TM) 64-Bit Server VM (17.0-b16 compiled mode):

"scenario2" prio=10 tid=0x0000000059d40800 nid=0x2014 in Object.wait() [0x00000000411bc000]
   java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
at java.lang.Object.wait(Object.java:485)
at tmtools.jstack.share.debuggee.WaitNotifyDebuggee$WaitThread.run(WaitNotifyDebuggee.java:23)
- locked <0x00002aaadcc67008> (a java.lang.Object)