Simple Benchmark:

Packets of sizes between 1 and 32767 are transmitted.
Client and service run on Sun Ultra1/140 and both
machines are connected with a 10MBit/s Ethernet.
I just measured the execution time of the client. 
The packets are just created and send to the server.
The server does not perform any actions on the
data. So the results should reflect mainly the differences
between the transmission. 

Client and service using MICOStream

real    8m24.113s
user    2m44.841s
sys     1m5.332s

Client and service using normal CORBA requests (not valid anymore,
since stubs/skeletons do not use the DII/DSI any longer)
 
real    387m28.150s
user    188m13.281s
sys     0m30.883s