I will release the results later in a separate document. However, as a summary
Apache ODE 1.1 is by far has the best performance, followed by ActiveBPEL 4.0. Oracle BPEL Process Manager is the slowest among the three.
It may not be a fair comparison, as both Apache ODE and ActiveBPEL are running on Apache Tomcat, whereas Oracle BPEL has its own application server.
However, for critical application, especially when high performance is required, and high load is expected, I would suggest that you go with Apache ODE, if BPEL is absolutely needed.
Oracle BPEL stands out in this area. Oracle JDeveloper can be used to develop the BPEL flow, which is very user friendly. Note that Oracle has its own extensions to the WS-BPEL standards. In order to make the BPEL flow portable among the BPEL engines, I would advise that you do not use it, unless you have a special reason.
ActiveBPEL 4.0 has a Eclipse-based designer. For Apache ODE, you can use the Intalio Designer, which uses Apache ODE as it underlying BPEL engine.