Well.. I think you have to write at least the bean class, because it is different for every application, and where your business logic resides. But, you are right, writing descriptors, interfaces is a pain.
I've been using
XDocletand it's great. Again, just write the bean implementation and with some javadoc-like comments XDoclet will generate all the other files for you (ejb-jar.xml,web-xml,interfaces -remote,local,localhome, home,and more! -) etc...
HTH