We are running SP4 in our Production environment and SP5 in our Dev & Test environments due to the same concerns you have - you made a smart decision to wait! The required Java upgrade is definitely not something we expected and had to resolve several environment related issues because of it. You will encounter this regardless of whether you move to SP5 or SP6. Also, if you use Documentum to manage your attachments, you will need to perform a Documentum upgrade as well. Beyond that, were not aware of any other known issues, but most of HP's software is always suspect (as I'm sure you know) so I wouldn't be surprised if we encounter further issues with SP6.'