JSESSIONID persistance

I found two page at F5 covering JSESSIONID:

 

 

Very simple:

 

http://devcentral.f5.com/wiki/default.aspx/iRules/iRulesCommonConcepts.html

 

 

Much more elaborate:

 

http://www.f5.com/solutions/deployment/websphere_v9_dg.html

 

 

I'm using Tomcat which also uses JSESSIONID in the same fashion I believe.

 

 

The WebSphere link goes through an elaborate setup of profiles and a more elaborate iRule.

 

 

Could someone in the know provide some commentary of what cases the simpler iRule doesn't handle?

 

 

thanks kindly!

 

greg