Ideally, there shouldn't be any issues in particular with struts or EJB 2 (websphere 8/x might need higher version of java to understand its own implementation but nothing changes for good old struts & ejb's). I never used Websphere in any case but what i can think about when it is server upgrade is there might be some class loading problems or dependency problems (redundant or missing jars) and (mis)configuration problems. However, take enough time and look into(read) the release notes and other supporting documents(migration guides etc..) for each release starting from 6-8(need not implement), just to make sure that you know little bit of every change in the release. Most of the times it is the silly mistakes which eats lots of time.
Since the question is in struts forum- There should not be any problems with struts whatsoever.
Whenever you encounter a problem, just post the exception stack trace in this amazing place and you will get it all.
Have Fun with Java
little,little.. little by little makes a lot..