Difference between office web apps 2010 sp1 and sp2?
please provide me the impact and steps for prevent the feature issues with the existed environment?
Service Pack (SP) is a roll-up of all previously released updates. SP2 contains all Cumulative Updates and Hot fixes before it, including SP1.
You can read Microsoft Knowledge Base articles: Description of the SP1 for Microsoft Office Web Apps 2010 (KB2460073) and Description of Office Web Apps SP2 (KB2687470) to learn more about the Service Pack.
The KB article lists the issues that are fixed by this service pack, and it also describes known issues or behavior changes that you may experience after you install this service pack.