Side effect of Service Pack for SAP XI 3.0

Hi,

Currently we are running on SP9, and want to upgrade to latest SP for XI 3.0 , At present my system is stable and mainly we are using XSLT/Message/Java mapping. Can you guys please tell me is there any possible side effect of upgradation so that we will take care of them.

It will be nice if you can provide checklist also.