I have seen more than 60% performance regressions for some RMI benchmarks sub-tests:
     Null/Boolean/Exceptions calls on server side

and big regressions for Exception calls on client side
(all compared to jdk 1.3.0).

To reproduce:

% uname -a
SunOS vispro 5.7 Generic_106541-16 sun4u sparc SUNW,Ultra-30

% jdk1.4/bin/java -version
java version "1.4.0-beta_refresh"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.0-beta_refresh-b70)
Java HotSpot(TM) Client VM (build 1.4.0-beta_refresh-b70, mixed mode)


% jdk1.4/bin/java -server -ms256m -mx256m -cp /home/zzhang/bugs/rmi-tests/rmibench.jar bench.rmi.Main

Null calls 32424.0
Boolean calls 23015.0
Exception calls 42701.0


% jdk1.3/bin/java -version
java version "1.3.0"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.3.0)
Java HotSpot(TM) Client VM (build 1.3.0, mixed mode)

% jdk1.3/bin/java -server -ms256m -mx256m -cp /home/zzhang/bugs/rmi-tests/rmibench.jar bench.rmi.Main

Null calls 16228.0
Boolean calls 10763.0
Exception calls 20287.0

similarly on client side:

% jdk1.4/bin/java -client -ms256m -mx256m -cp /home/zzhang/bugs/rmi-tests/rmibench.jar bench.rmi.Main

Exception calls 46280.0

% jdk1.3/bin/java -client -ms256m -mx256m -cp /home/zzhang/bugs/rmi-tests/rmibench.jar bench.rmi.Main

Exception calls 20399.0