Hi Boris,
I'm not sure, if you're looking for the same thing as I understand under "jBPM plugin"... I understand it as the BPMN2 process designer integrated into eclipse.
If it's what is shown on the sshot below, then the answer is yes, I have it installed... unfortunatelly, I don't know about other designers - even the webbased Oryx doesn't work on my setup (there are known compatibility issues with nearly all web browsers - IE does not and will not work, FF not, chrome, which should work also does not... I think, someone claimed, opera is OK?). I think, the webbased designer is a way to go, but it needs some more time...
http://community.jboss.org/servlet/JiveServlet/downloadImage/2-582448-11177/450-260/Screenshot-Drools+-+SimpleTask-src-main-resources-Simple2.bpmn+-+Eclipse+SDK+.png
