No problems with WebLogic, the only issue is that WLS has a configurable
Classloader behaviour and, by default, is not the one used by Tomcat
(with WEB-INF/lib before System Classpath). 
Infact it's enough to use the <prefer-web-inf-lib> tag in 8.1 (or the
appropriate flag in 6.1) and all will works great !!!!
Hope this can help.
L.