I just tried upgrading from 1.9.0 to 1.10.0 on an Ubuntu server and deleted the work directory under tomcat6 as mentioned in the instructions.
When trying to restart tomcat6 service I encountered an error saying it couldn't create the work directory so I manually created it and tomcat started.
When browed to the page I get a long error but the part that jumped out was:
java.io.FileNotFoundException: /var/lib/tomcat6/work/Catalina/localhost/_/org/apache/jsp/index_jsp.java (No such file or directory)
In this case I'll probably just start from scratch but I'm wondering if I did something wrong or if the instructions are wrong?